[mpetroff]

It applied a linear transform to RGB values, like the current method, but the original matrices were the "colorjack.com matrices" [1] that have been floating around the internet for a while. They weren't derived scientifically and are quite inaccurate, at least for protanopia.

[1] https://github.com/MaPePeR/jsColorblindSimulator#the-colorma...