If you are not suffering from a color vision deficiency it is very hard to imagine how it looks like to be colorblind. The Color BLIndness Simulator can close this gap for you. Just play around with the sample picture or upload your own images. Please make sure that you just use JPG, GIF or PNG images with a size below 600kB.
As it is not not so easy to describe color blindness it comes in handy, that some smart people developed manipulation-algorithms to fake any form of color vision deficiency. The algorithms transform any picture into the same picture as seen by red-, green-, blue- or completely colorblind people.
I would like to thank Michael for providing the color blindness matrix and Luz A. for taking the photo, which is a great sample picture to show the effects of the different forms of color vision deficiency.