The other day I posted about reproducing the effect of the synthetic quills with different coloured threads. Here is one that is made from Tan and Black UTC threads, and coated with Diamond Hard UV resin. I've tied these as basic dry with a collar hackle, but no wing. You could use this any way you like.

And to give you an idea of the sort of effects, form Left to right, Adams Grey / Black, Tan / Olive, Tan / Black, Olive / Black, Green / Black.

You can get colours from the very subtle (Tan / Olive) to the very brash (Green / Black). It may tax your thread control at first. Once you get into the swing of it they are easy enough. One advantage of this is there is no problem using them for larger flies than can be tied with quills.
Cheers,
A.