It's hard to tell from the picture with the grow light on because the soil looks purple too. You might want to get a pic in white light.
I think there are a couple things that can cause some purple color. Cold can do it and really dark green(but healthy) leaves from lots of N can have a purple tinge(mine do). P deficiency can too but I don't think it usually happens this early. It usually happens during flower. Oh, and I think some strains can have purple.
I don't think the light would do that but I don't know for sure.
I know it's not the advice your looking for but at least some things to consider until someone smarter chimes in.