You can either split wool tapestry lengths down from 4 to 2 filaments, choosing "off" (ie grayed for blues, earthy for reds, yellowed for greens or muted) or plant colours if you know the colours achievable.
Often you see bundles of leftover skeins coming up on ebay which is a cheap way to start a stash, ( but you can't guarantee matches as although numbered, not all colours were continued, nor are dye batches utterly constant, which can be taken advantage of in yer chat if you know about natural dying). If you are prepared to buy odd lots, you can build a large selection quickly, bearing in mind one new 8 -10m skein would cost you 65p each. http://www.ebay.co.uk/sch/i.html?_odkw= ... sacat=3104
Pre-cut leftover lengths from tapestry kits are also a good buy.
OR if you have access to the right colours in pure knitting wool leftovers, bag those and split down - split threads will need a slight twist and a bit of beeswax, like the blanket ravellings.
Or you can PM me, as I said