These days I think getting into open source is great advice for minorities, and I think they will find it to be as close a meritocracy and "color-blind" environment as they will find in America today. That said, it is an inherently harsh environment to learn where there is a pretty low tolerance for beginners, and it could be quite discouraging for someone just getting their feet wet in programming. Also, if it's pitched heavily as a gateway to a lucrative career by parents and authorities a lot of people are going to be pushed into it who might not have the intrinsic interest to succeed in the pedantic world of telling a computer exactly what to do.
That said, one has to imagine that the number of blacks and latinos with a very strong potential to be good programmers is probably severely under-represented in industry as well as open source simply due to lack of early opportunity and privilege.