IBM EGA colors in 350 scan line mode are 2:2:2 bits of R:G:B, stored in memory as xxR'G'B'RBG. That's 3 low-order bits followed by 3 high-order bits. IBM CGA colors are 4 bits stored in a byte as xxxxIRGB. (EGA colors in 200 scan line modes are the same as CGA colors, but stored in memory as xxxIxRGB.) That's 3 high-order bits (one for each of R, G, and B) plus one low-order " Intensity" bit for all 3 components R, G, and B. Exception: IBM monitors show IRGB = 0110 as brown, which is really the EGA color R:G:B = 2:1:0, not dark yellow 2:2:0.
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