I had a foxface a while (until it out grew my 45g) i bought it very small and just recently traded him back to lfs. I'll really miss that little guy. I think they are a great fish with great personalities.
Yo will find them very hearty and fun to keep. Feed them plenty of seaweed selects and nori on a seaweed clip.
As trey said, this is normal for them to turn very freaky colors at night.
This is their camoflage. Hope you enjoy your new fish.