Can't believe nobody mentioned colourblind readers. I'm not into the political correctness thing at all but if you want to have as broad an audience as possible, this is the way to go.
From "The Elements of Statistical Learning":
Our first edition was unfriendly to colorblind readers; in particular,
we tended to favor red/green contrasts which are particularly troublesome.
We have changed the color palette in this edition to a large
extent, replacing the above with an orange/blue contrast
Thanks for the note!
I did mention colorblindness in the article.
In case you missed it here is the quote:
"Colors can be hard to distinguish from one another. If you have colors of similar hue, it can be difficult to tell them apart. In addition, you might prevent those who are color blind from understanding what you are communicating."