I think Neddo must have the same problem I encounter in Spain: there is no colored fondant to buy at all :-(((
Here is how I solved this problem and get any dark colors I want with no mess:
I mix a little quantity of gel with s powdered color (food coloring, not dusts) Any hydro soluble one will do, not the oily ones for chocolate!
I do the mixing directly on the fondant with a spoon. The gel will help the powder to dissolve. I knead once, then wrap it and allow the powder to flourish overnight.
I then give it a good last knead the next day et voila! Perfect reds, blacks, navy, dark greens.
The lack of goods makes us creative ;-)