I played infected for the first time today.
I wasn't sure how the game should be played, I gave a particular attention on minimap.
I saw at least one "doubled" green triangles (teammate). I thought it was because he got infected...
Later I played a Team death match KC and I saw the same doubled triangle.
What does it mean ?
Edit
Here's a screen shot of this video.

Why the teammate pointed by the red arrow appears differently ?
