A couple thoughts.
Living Colour got a lot more attention from the media on their debut album, and second album, in comparison to Extreme's first record. Living Colour was really spotlighted at the time because they were an all-Black hard rock/metal band, which AT THE TIME, was a bit of an oddity for the genre. In addition, Living Colour wore is politics on their collective sleeves, talking about issues facing Black men and women.
But as time went on, and Extreme hit big with Pornograffiti, they eventually eclipsed Living Colour. Particularly since Living Colour split up in 1994, and didn't reunite until 7 years later. Yes, Extreme broke up in 1996, but Gary Cherone fronted Van Halen, and Nuno was doing his thing on a larger scale, so that contributed to Extreme still being "more popular" even when not as active overall. Sure, Living Colour bassist Doug Wimbish played (plays) for some huge acts (just like Nuno), but apart from him, the other Living Colour guys really just stayed local and did small time projects here and there (and still do).
But in the 1988-1990 timeframe specifically, Living Colour was by far more popular. When Extreme put out their second record and it blew up, they ultimately eclipsed Living Colour in terms of worldwide popularity, and that continues to this day. Both bands, however, have similar qualities, and really are outstanding live acts.