Ya, I'm kinda tired of running out of my cover when some teammate throws a nade on the floor and I think "OH SHIT GET DOWN" and I get shot while running away. If it had my teams color I would think "Just some idiot/griefer spamming nades again."
It's also useful when somebody is spraying with his SMG "Should I take cover for it? Or can I simply walk out?"
The tracers should also be colored on the minimap. Grenades don't have to be shown on the minimap. It'd ruin the element of surprise. This would mean the voxels with the teamcolors on it have to be made black. But safety first, children!
P.S. I saw colored tracers being used in Operation Flashpoint, U.S. Army probably does this too.
P.P.S. Disable grenade damage on blocks put by your team. So you can teamkill griefers.