1980's-era graphics esoterica
In the days of 8-color displays (or 16, where the the second half was just brighter versions of the 8), I never saw a pattern in the order the colors came in for things like ANSI X3.64 codes. I assumed they had their small set of colors but the order was arbitrary.
But 8 is how high you can count in three bits: one bit each R, G, and B. The direction may differ between implementations; looks like ANSI X3.64 has Red as the lowest and CGA has Blue as the lowest. But the order of the colors just comes from counting up in binary.
0 0 0 - black
0 0 b - blue
0 g 0 - green
0 g b - cyan
r 0 0 - red
r 0 b - magenta
r g 0 - ~yellow~ brown?
They made a special case for brown, where the green bit only counts for half, because they thought it made a better palette than a dull yellow: https://en.wikipedia.org/wiki/Color_Graphics_Adapter#With_an_RGBI_monitor
Never would have guessed they went to extra expense for that CGA brown!
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