I heard on television once, on one of the various cooking/chef shows I was watching at the time, that to preserve the color or the green-ness and not have black basil (if you put it in the freezer) here's what you do. You should take a sizeable amount, a few handfuls in the blender, and with the small amount of olive oil as a medium for it to freeze in, then should toss in a single vitamin C pill into the blender. The asorbic acid keeps the herb green.
Sure everyone knows that if you simply toss fresh basil into a zipper bag and then into the freezer , the basil blackens. I have also used a small tiny bit of water, again, as a medium for the basil, put it in the blender with the fresh basil leaves, made a thick (sauce?) out of it, then put it in ice cube trays or individual packages of 'seal-a-meal' bags. You then have your small portions for when you need just a little. It's not seasoned, so you do that according to what you need the basil in/for. All that basil goes to work for you during the winter when it's not available, or is, but it's stupid expensive.