coraline?

Little pretty green, pink, and purple dots. Won't scrape off.

The green dots are probably the start of algae - I got them too when I started my tank, and before I knew it I had a full blown hair algae outbreak. That cleared up pretty quickly though and hasn't come back. The red dots may be the start of coralline. I got those two and they are still just dots, but I'm still hoping they'll become a nice coralline some day! The purple ones I have no idea LOL

I think it's all coralline. Green coralline is pretty common.

I lot of my Coraline started off as green. As it matured it went to the various stages of purple.