[Glows]
when some is glowing, they have a colored translucent field around them, so it is hard to tell which team they are on. In Q2CTF, they blink, giving you a chance to see their skin, and in LMCTF they are different glows for different teams.

If you see someone glowing blue...
Hide! This dude's got the quad! Get out of his line of sight and let a rocket loose. But make sure it hits him. Nothing worse then when a quads mad at you. Well maybe one thing...
If you see someone glowing red...
Run! Don't walk, run! Invulnerabilty! Unless you know know this guys got some serious armor on, don't even bother shooting at him. Just wait for him to start blinking and let loose some rockets. (Note: They took invulnerability out of Q2CTF, but it's still in LMCTF)
If you see someone glowing pink...
Pray he didn't see you. This guy is not only Quaded up, he's packing some invulnerability too. This is rare, but when you see one of these, go to the other end of the level.
If you see someone glowing green...
when you shoot him, he blinks green. When he falls a considerable distance, he blinks green. They're wearing power armor. If your lucky they'll be stupid and try using the Hyperblaster or BFG (maybe lucky isn't the right word...) they'll be easier to kill, since they're using cells to fire, and when you hit them they lose cells. The best idea is to get in, take your shot, and get out. These guys can take some serious damage, but they'll still killable.
If you see someone glowing white...
You should realize you should've used that nifty feature on gamespy to filter out servers using cheats. He's got God mode on, so your only hope is to use you shotgun and knock him into someting that'll kill him. (not much! The coolant in the reactor level will, but that's pretty much it. For pushing someone, use the Super shotgun. Or, the famous telefrag. It's hard to do, but you have no idea how proud you feel when you telefrag the god moded enemy flag carrier) if you can do this, be proud. It's cool, even if you didn't get the frag credits. I don't condone cheating, but if you want to sneak up on that God mode guy, type "notarget" in the console. I don't know if the can see you after you frag them, but it's worth a shot. Personaly, I'd go play on another server.
Or...
I was playing LMCTF the other day, and on LMCTF02, I saw people glowing white. When this happened, I didn't find cheats on. I was confused. Then Cousin Randy enlightened me. It means they have invulnerabilty. Plus, when the red team picks up quad, they turn red, blue turns blue. They must've done it to keep people from getting confused.

Disclaimer: Glows can be used differently by different mods. If you see someone glowing white on a Freeze Tag server, they're not cheating, they're frozen. In Jailbreak, when I red guy picks up a quad, he glows clear. The above work for Q2CTF, and eventually LMCTF.