With the colourtone I'm assuming it's pre-mixed. The stuff I have was premixed in water I think. Most of the stains are either in water or alcohol. Your idea of shellac in metho is probably your best bet with what you have. Another possibility is mixing it with a water based poly. In my case I use a water borne custom paint system that's poly based, and would mix in a dye based product known as a candy colour. There are also stained polys you can get, but they are usually timber tones. no toxic green or candy apple red in those lineups!