What Happens When Two Galaxies Collide?

When galaxies collide, gas clouds slam into each other. This means new stars will form there. But it's not from the stars themselves colliding. It's from the gas and dust colliding. These aren't really colors, are they? Wer look, how are we seeing this? Because everything in this picture is not what our eyes could see. And then we color cot it in ways that our eyes can see so that we can appreciate it.