While the difference between red and green is blaring to most of us, it is imperative in good design to think about users who aren’t like us– say, users with color vision deficiencies. This is where redundant cues come in, a specific method for adding accessibility to a product.
Redundant cues give a user multiple ways to take in information and therefore make a design intuitive and easy to use for a more inclusive audience. Especially because color blindness affects 1 in 12 men (8%) and 1 in 200 women (0.5%) in the world, reinforcing cues with something other than color is very important . Examples of redundant cues include the old Apple chat interface (as shown in class) :
SOURCES: http://www.colourblindawareness.org/colour-blindness/  Dictionary of Design Concepts by Krzysztof Gajos
Contributed by Allison Lee, Megan Ross, and Justin Hunter