I've submitted a script to the script server that makes that really easy to do. It's not approved yet, but it's script #177 so you can get it if you know what you're doing (and if you trust me enough (you shouldn't, see my username)).

If you had that installed, it'd be as simple as

tpt.all():eq("ctype", 0xDEAD):set("dcolour", 0xFFFFFF00) -- paint particles yellow whose ctype is 0xDEAD