I did this last night (the red row isn't finished yet).
I'm using a 5mm hook and various DK to light worsted weight yarns from my stash. The grey at the beginning will the be most represented, as I have four balls of it to spread out. I'm grabbing yarn at random, so we'll see how it progresses. So far, I like it.
I chained 219 for a blanket just over 60″ in width. My loose calculations say each pair of rows uses about 60 yards of yarn, so my 15 balls or so will yield more than I'd originally thought. Phew!