Add a little CMC (Tylose).
If you want to avoid colouring vast amount of fondant (as well as having the health benefit of not consuming lots of colouring, try this:
Colour about half the fondant you want to use and take a similar quantity of white. Partially roll out each lump of fondant to a similar size. Place the coloured piece on top of the white and continue rolling. You will end up with a sheet of coloured fondant, backed by white, which no one will see until they cut into the cake. The one disadvantage is that you only get one go at it, so make sure you make it big enough! (It works really well with The Mat too)