Even if you were unable to see ANY color, you could pick strong and weak shades of gray that would help you parse visually.

No, it really doesn't work that way. To disambiguate certain colors (and especially shades), I have to concentrate specifically on the colors to the exclusion of everything else.

If using specific colors helps you personally, that's fine--but it slows me down measurably and raises my frustration level dramatically.

My friends and I have gone as far as to mark all playing pieces in board games to disambiguate colors such as brown and green. Green pieces have little white dots, for example. Otherwise, I won't play because I spend too much time trying to distinguish the colors of individual pieces when everyone else can glance at the board and see what's happening.

Again, if using specific colors helps you personally, that's fine--but despite red-green colorblindness affecting a statistically significant percentage of men in the world, the default choice of colors nearly always mixes red and green if there are more than two colors. I have my doubts that I could use any system that used color coding at its default settings.