Yep! Mix and match all you want!
Just make enough so that you don't run out. You will almost never be able to match your creation perfectly with a second batch of ink. Use the extras on a small run or mix it with something else later.
I store my extra ink in leftover yogurt or butter containers. Just put a piece of plastic wrap between the cup and the lid and you're good to go for a few months.
Enjoy
