The rocks will gain the coralline color over time, IMHO grab a few pieces that are covered in it, and the rest base rock, when they come rub the good pieces on the base rock and watch it start to grow over time. No since in paying all that money for something that will occur naturally.
Ive always been a fan of letting the tank develop itself. My LFS sells corals on nice size rocks for only a few dollars more than the 1" frags, i prefer the frags that way they grow into the tank and develop its look on itself.