Good question. In some other analyses it looks like interventions that are designed for and delivered to African American MSM work well. But in most of these studies, men of color were only, say something like 10% of the sample.
The problem may be that for various reasons, the men of color in majority white studies feel isolated and don't feel like the intervention is really addressing them. For example the characters in videos may be white, or most of the people in their small group meeting are white, and they don't feel like they are facing the same set of issues, so they don't connect as well.
I think as a gay man I often feel the same way about messages for straight audiences. It's not that I don't like it or whatever, it just doesn't seem to apply to me. If I know the message is for me, then I'm brought into it and get invested in following through.
Just a hypothesis for now ...
Gotta run - hope you're having a good evening Miz Jess!!