Arc-En-Ciel = Rainbow
For week 8 dailies
Those colors are subject to changes but should remain around the same.

Yes you can use, if you use the exact same colors an inspiration credit is nice so I can see how you used them trough mentions
But you don't really have to credit since colors can't be copyrighted, except Coca Cola's Red which is XD

http://rika-dono.deviantart.com/art/Arc-En-Ciel-Palette-573832655