hey, I had the exact same problem, and I found a very simple answer.

say you want to send certian text to the rtb, like when <Joe> says something...

with RTB1
.selstart = len(.text)
.selcolor = vbBlue
.seltext = "<Joe> "
.selstart = len(.text)
.selcolor = vbRed
.seltext = " hey this works great!"
end with

you can easily make a sub for it so you can do something like Call Color(vbRed,"Hey") or something like that, thats what I did.