Well, after much consideration & typically with me, getting a bit fidgety with everything running smoothly
rolleyes
, I fancied rooting my phone.
Didn't want to go for the Sense ROM yet (too early and many bugs), so stumped for Cyanogen's latest Vanilla ROM build.
The process was a bit nerve-wracking for a non techie but managed to follow the written and video guides & hey presto, the trackballs glow different colours! I think the only one I can now change is the Messaging colour (haven't yet worked out how to manipulate the other ones.
Phone runs faster as well, plus I have wired tethering to a laptop using the phone.
See the thread at the top of the Nexus One forum if you want to find out any more.