This app was mentioned in 4 comments, with an average of 2.25 upvotes
Normal humans with 3 cones see a hue rainbow with complete differentiation between all hues. Someone who is colorblind, with 2 cones, would see certain discreet chunks of that rainbow matching each other, and in a color a 3-cone masterrace would describe as some form of brown/grey.
Now, the thing is, 3 cones already covers the full spectrum. So gaining one more, you aren't gaining whole new colors that a 3-coner would think are the same. The cone would be overlapping some part of the spectrum, so for that section you'd just have much greater differentiation of colors than your average guy. It'd help for Blendoku, I guess.
Blendoku 1/2 is a game that plays on this! I suck at it but maybe some of you out there can be a prodigy at this!
For anyone reading that wants to get sorta good at seeing very small minute differences in hues, play this game.