Think of colorblindness as a measure of inability to discern contrast between an image and its background. Nearsightedness, too, can impair one’s ability to distinguish color from afar (for example, from 10 feet away), and so can excessive amount of light in the room.
Colorblindness is yet another reason not to base your design just on color. Colorblindness comes in three main forms:
Do not rely exclusively on color to differentiate classes and status types. Instead, supplement your design with additional graphical elements and shapes. Instead of guessing whether a particular color scheme would work for colorblind users, let them customize the colors:
Tip: Turn down your television saturation to zero (grey scale), and test your UI from 10 feet away. Maintain enough contrast between the fonts, icons, and background.
To make your game more accessible to players, it is highly encouraged to implement an option within your setting menu that changes UI and HUD colors to accomodate the different forms of colorblindness.