Think your snazzy new UI is fantastic? Did you test it with color-blind users? No? Then you’re probably in for a surprise for how much information you are trying to convey in a way that is not accessible to your users who have colorblindness or color sight deficiencies. We will discuss the details of what it means to be color blind, some clinical details of the condition, and what you can do as a programmer or designer to improve the usability of your software for the 1 in 12 of your users who have a color deficiency.