It's normal, your rocks are going to turn all sorts of colors before they turn purple from coraline.
[emoji115]all sorts of colors is right! Brown to red to green back to brown, a little purple, back to green and then purple is how mine is going. Pure white, new rock is PERFECT for growing all sorts of algae. Expect it for a few MONTHS to come. Coraline is finally exploding in my tank @ the 6 month point. Enjoy the journey!