I can't stand when there's a trip mine grenade in front of me and I don't know who's it is. Sure you can shoot it, which I often do in case it's the enemy's. But wouldn't it be great if it flashed a different color for teammates? I vote for green.
EDIT: Apparently the grenade shines white instead of red when it's friendly. I can't tell... Vote up if you think it should still flash green!
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Agreed, I can't tell you how many times I've avoided corners because there was an unidentifiable explosive waiting there.