Not the sRGB used in monitors and simple color-pickers, no? Might be wrong here, but I'm fairly certain that day-to-day RGB that most programmers are familiar with is a direct representation of the brightness of the various colors of pixel in a given region (modulo green). The CIE-XYZ color space is the one which tries to represent human vision. RGB isn't crazy far off, but the R, G, and B values certainly don't map directly onto the activation of the L, M, and S cones. (0,255,0) is legal RGB, and displays a particular color, even though such a combination of activations is clearly impossible in the human eye. So given that RGB is a simpler, more tractable representation of a more complicated system...I'd call that an abstraction.