Beautiful, accessible traffic light colors

design

Cross-posted from my Medium blog.

Gorgeous red, yellow, and green autumn leaves from enneafive of Flickr
Autumn leaves showing off a glorious red/yellow/green palette. Photo by enneafive of Flickr, under Creative Commons by 4.0 license. Links below.

Everyone uses them: Green, yellow (or orange), and red. We use them in data visualization, we use them in buttons, we color text and icons with them and put them into alerts. They are often used in crucial moments, when we are announcing success, or breaking bad news. We abuse them, too, using them to draw attention where they aren’t relevant. What we don’t do, far too often, is make them accessible.

A significant minority of people are color blind, and most of those have red-green color blindness. Since 2011 I’ve had to solve for color accessibility in important interactions, such as alerts for patient vitals, quality of patient care, cloud server status, or executive sales analytics. Here are some accessibility tips I’ve picked up along the way, as well as my personal template for a usable, accessible traffic color palette.

Use icons as well as color

You may design a beautiful, color blind-friendly palette, but it never hurts to reinforce the message. Instead of changing text to red or green, put a differently shaped red or green icon next to the text. That way, even if you have no control over your color palette, or the chart has been printed in black and white, or your user sees only in grays, you’ve made your point.

Case in point: Excel. Excel offers icons in traffic light colors to help tell your data story. Make sure you use differently shaped icons as well as different colors! Here’s why:

Normal and colorblind comparison of cons from Excel, Office 2013
Desktop Excel, Office 2013. Pay attention to the red and green circles — could you tell them apart easily? Microsoft resolved this issue in later versions.

Deuteranopia and protanopia are two common types of red-green color blindness. Testing your colors against them will optimize for most of your users, but icons help seal the deal.

Don’t trust preset color palettes

There are many extremely useful frameworks and boilerplates online. Each meets many needs, but not all have had the time to optimize their colors for color blindness.

Popular present color themes that fail colorblindness accessibility
Examples of popular preset color themes that didn’t check for accessibility in color usage. (Or, “Why not to use orange.”)

The most important question when looking at your reds, greens, oranges, and yellows is, “Will my users recognize this color when they see it by itself?” Don’t trust the people who created your framework to have thought of this. Check it out for yourself.

Common colorblindness checking with Adobe

How do you do that, you ask? For many years the only solution I found for testing was Adobe’s PhotoShop, which offered protanopia and deuteranopia views of whatever I was creating. The options are under View → Proof Setup (see image below).

Path to colorblindness previews in Adobe Photoshop
Screenshot: finding the colorblindness previews in Adobe Photoshop.

Recommended online colorblindness checker

The Corblindor Coblis (Color Blind Simulator) is now my go-to tool. Just do a quick screen shot of your work, and see how it looks for many different types of colorblindness.

Plan ahead with a color template

I’ve done a lot of data visualization color work over the years, and a pattern has emerged that I find helpful. I’m offering it here, in the interests of making data more usable. I strongly recommend considering this approach when you’re developing a brand color palette.

Example of an optimized set of traffic colors, with colorblind views.
Notice how light vs. dark and warm vs. cool differentiate the red and green. Your yellow should be significantly lighter than either your red or green!

Here are the key guidelines:

  • Use a light, medium, and dark shade. Your yellow should be your light shade.
  • Use a warm green and a cool red, or a cool green and a warm red. Just don’t have both cool or both warm.
  • No orange. Because it’s so much lighter, using yellow instead of orange makes it much less likely your “warning” color will conflict with your “success” green to color blind users, or look too much like your “serious problem” (errors, e.g.) red.

That’s it! Thanks for reading. Go forth and have fun telling good stories with your data.

Venn pie-agram

fun

Love data visualization? Love pies? So do I.

Venn pie-agramPumpkin + pecan + apple pie crumble = Venn pie-agram

Last Tuesday we had a Thanksgiving potluck at work, and at the instigation of a coworker I made a Venn diagram pie. Here’s how I did it, if you want to try it yourself.

What you’ll need

You can use whatever flavors you want, but remember they have to combine into a pleasing flavor profile. The flavors of the three ingredients I used were pumpkin, pecan, and apple crumble.

The recipes were fairly straightforward. Since the undertaking was complex I went simple with the recipes. For pumpkin and pecan filling I adapted About.com’s Southern Food Classic Pumpkin Pecan Pie recipe. For the pumpkin filling I bumped up the ginger and added nutmeg. For the pecan filling I used dark corn syrup, replacing about 1/3 of the dark syrup with maple syrup and a little molasses.

For the apple pie I used Cortland, Gala, and Honey Crisp apples. (I recommend The Apple Works for good information on what apples work best in what contexts.) Once again the About.com Southern Food section provided a good Apple Crumble Pie recipe.

I’d never used it before, but Pillsbury’s rolled up pie crust did pretty well!

So, to make this happen you need the following:

  • Two sets of aluminum cake or pie pans (4-6 pans). Cake may allow you to overlap the three pans and the middle section more easily, but pie works, too. You’ll need three pans for baking, and at least one extra to make the middle crust.
  • Aluminum foil to cover the pie plates and prevent leaks. You’ll also need it to protect the crust while baking.
  • Enough pie crust for the bottom of four pies. This will cover the three-plate section, provide crust for the middle, a base to hold the middle pie crust in place, and a little extra in case you want to add decorations.
  • Pumpkin pie filling to taste.
  • Pecan pie filling to taste.
  • Apple pie filling to taste.
  • Crumble mix (no pecans to start).
  • Pecan halves for topping and to add to crumble mid-way.
  • A cookie sheet to support the pie plates, which will not be structurally sound enough to support the weight of the pie.
  • Two six-packs of graham crust mini-pies (for excess filling).

Making your Venn pie plate

Here’s how the three pans overlapped. Note how corners are folded over. I used an ancient pizza pan for support instead of a cookie sheet (most cookie sheets don’t fit in our tiny oven).

Three overlapping pansMaking the superset framework for a Venn pie-agram.

A detail from the bottom. Cut your flattened sides into sections so they lie flat and don’t warp your pan.

Pans, bottom detailDetail, cut and overlapping sides.

Line your completed pan with aluminum foil to cover the sharp edges you’ve cut and prevent leaks.

Aluminum foil liningAny experience with tin foil hats helps in this step.

Making your crust

Preheat your oven to 350°.

Unroll your pie crust and lay it out. Cut away excess and press edges together so you have a continuous bottom that isn’t too thick.

Pie crust laid outKeep your excess pie dough!

What not to do

The image below, with raw dough and supporting aluminum, does not work. The crust melts and doesn’t hold its shape. Thin metal dividers also do not work: they leak abominably. I learned this making my first “pie chart” pie; metal dividers were much more trouble than the crust below (for one thing, I had to tilt the pie in the oven until the pecan filling set).

Don't try this in the middle diagram area. It doesn't work.Little metal dividers not only leak, but the necessity of removing them before eating would ruin the pie.

What works

Partially bake your pie crust edges and bottom about 10 minutes at 350°. Also bake sections for the middle crust, separately (see below). Note that the middle crust has a slightly tighter curve, to make the overlapping areas slightly egg-shaped instead of pure circles. This will give you more space in the middle sections. Don’t forget to puncture the crust with a fork to avoid bubbles!

Important: reserve extra unbaked pie crust. You’ll need it to make the middle section work properly.

Middle crust sectionThis piece will form part of the crust defining the overlapping sets in our Venn pie-agram.

These are the crust pieces you’ll need to shape the middle of your Venn pie-agram. I used six crust lengths: one long curve, one not-so-long, three short ones, and one tiny one.

Venn pie-agram diagram
Super-sophisticated Venn pie-agram wire frame.

To make the crust stay in place and reduce leaks, use unbaked dough to hold the partly-baked middle sections in place. It doesn’t need to be perfect. Tip: Use a bread knife to gently saw the pie crust sections. Pie crust is crumbly. Try to make them line up naturally with the outside edge.

Middle crust section installedThis is what your middle should look like. It’s not perfect circles, but trust me, you’ll prefer this when creating your overlapping fillings.

Filling and baking

Tip: Start with the firmest filling first. It will fill up any weak spots a more liquid filling might break through, keeping your sections more compartmentalized. Here, the apple pie section has been filled and covered with crumble; apple has been layered in the bottom of its three overlapping sections in the middle. To the right, pumpkin filling (my next step). The pecan filling is in the center; pecans have yet to be added. I used crumbled pecans for a thicker mixture. Pecan filling went in last.

Pie workspace and fillingsUse baking time to clean your workspace! (How else will you have room for photos at the end?)

Here’s how I did the fillings, in order:

  • Apple crumble
  • Apple covered with pumpkin filling with normal crumble (no pecans)
  • Apple covered with pecan filling
  • Center: Apple covered with pumpkin filling with pecan crumble (I added pecans into the food processor with some of the crumble mix)
  • Pumpkin
  • Pumpkin covered with pecan
  • Pecan
  • Cover the pecan area with pecan halves; place pecan halves in the three pecan-containing middle sections

Ready to bake! Note the aluminum foil protecting the edges from over-baking. You can see some of the mini-pies I made using the excess filling.

Ready to bake pieOn its way into the oven!

Results

The pie baked about an hour before a knife came out cleanly from the pumpkin filling. The mini pies, which I baked after the pie, took about 35 minutes without a cookie sheet. Oven heats vary, so check your pie at around 45 minutes, and your mini-pies at 25 minutes.

Venn pie-agram and mini-piesA Venn pie-agram triumph! Or, the mother ship and her fleet. Whichever you prefer.

Have fun!