Nope, doesn't appear to be in the manual.
If you haven't installed the v1.11 patch, Ironhand's Su25T Orientation training track will tell you a whole heap of useful stuff about the Su25T, including the meaning of the tank lights.
If you have installed the v1.11 patch, look at rolling back to v1.1 for as long as it takes to watch the track - it's worth it for what you'll learn :)
(in case you're wondering, no, tracks don't play back correctly between versions)