I think some of the "raspberry" figs like Bordeauxs, col de dames, and adriatics contain anthocyanins, sort of like blueberries and red cabbage. This probably gives a more rich appearance because this anthocyanin used to be used in natural dyes for clothing, etc. ( red, magenta and even purple). I agree also that some color contrast may be due to time cooked but I think a lot of mt. Etnas lack the anthocyanin, too.