Some individuals have a perception of colors different from what most people see. This decreased ability is called color blindness or color vision deficiency.
When you design a slideshow/poster for a presentation, a figure in an article, a flyer ... it's important to keep that in mind and try to make your design accessible to everybody.
Roughly 8% of men and 0.5% of women are Color Blinds. It's a lot right?
You would not want your design to be un-friendly to that many people?
The main cause of color blindness is genetic and so far there is no treatment.
The human retina contains photoreceptors: the rod cells, responsible for low-light vision and 3 categories of cone cells, sensitive for the long- (red), medium- (green) and short-wavelengths (blue) of the visible light.
In case of color blindness these cones may be deficient or absent.
|2 or 3 Cones||Monochromacy|
Deutan: Unable to distinguish between colors in the green-yellow-red section of the spectrum.
Protan: Also unable to distinguish between colors in the green-yellow-red section of the spectrum. And the brightness of red, orange, and yellow are much reduced compared to normal. Reds may be confused with black or dark gray.
Tritan: Blue-indigo-violet are seen greenish and drastically dimmed, down to black.
Monochomats: Totally unable to see colors.
By example red-green color blinds (Deutan and Protan) can't tell if a banana is ripe or see a red-berry in a tree.
Regarding design, it might be difficult for them to name a color, to associate the color in a caption to the one in the figure, to distinguish to or more colors from each other, or it might be impossible to simply read Red text over a dark background.
Here is a simulation of what a rainbow of color looks like for colorblinds:
A good design increases accessibility for colorblind. Here are some suggestions to be color-blind-friendly.
NOT THE BEST