Blue Coralline?

[meeandcharlie]

When I purchased my tank I received live rock. I kept it cycling to keep it alive while my tank was set up. A couple had bluish colors. One in particular appeared to have almost a navy blue. If it's not blue it must be a deep violet. Crossed my mind someone had painted it as it was so unusual. Probably the case! Attached a photo (tired to attach a couple for reference but my uploads failed), color is pretty close to what I see.

[JUNBUG361]

Yeah it's coralline algae with some green hair algae

[juniorrocketdad]

Blue coraline is real just much less common

[EdgeN]

I haven't seen it yet.. Our tanks go through a lot of changes at first and all kinds of colors show up, but I don't think I've ever seen a mature tank with a nice patch of blue coralline algae growing. It's always kind of of blue, sort of blue etc. This color would be a hot commodity on some rocks I would think, unfortunately it's no where to be found.