She keeps a large hard plastic "salad" bowl next to where she sprays. She takes her large scraper and runs it across the sprayed mold. Then scrapes off the excess color. Then she scrapes it against the edge of the bowl. She works her way around the edge of the bowl when she changes colors. After it sets up, I break it up and put it back in the bottle. Sometimes it is a bit hard to stuff it back in, but you could always remelt each color and pour back into bottle. I'm amazed at how much color you can save, I looked back on video from /vegas workshop, and Lionel is doing the same thing. I tried to post video here, but I don't know how to change it from a .mov extension to an acceptable one.
I did a screen shot. You can see a small amount of color on the edge of the bowl.