Hey guys, when the green horn appears in your screen, what does that mean?

Hey guys, when the green horn appears in your screen, what does that mean? I’ve been playing the game 2 weeks now and have only seen a red horn…

When I press on the green horn, there is a watch icon, or go to icon and then there’s a red eye… If I press the red eye, would I attack my own alliance? Which obviously want to avoid.. or is that to help my alliance with an attack? I know when the red one appears it’s because an enemy is heading your way.

Thankyou for your help!