Might be a bit 'spensive for a full blanket - might look into natural dyes as muddy colour is fine (anything better than pink!)
Cheapest floor sweeping tea or teabags you can find, stronger the better and brew them up as strong as you can. Make sure you've got the wool as clean as you can and it's still sodden wet and then put it into the dye. I use a big black bin so that I can move the fabric around in loads of water. It's wool, the tea is tannin, even if it ferments slightly it won't rot the wool if it's left soaking for a week, it'll just slowly reinforce the dye.
Tannin doesn't need a mordant (a fixative) and it'll change that pink for you to a brownish colour of some sort.
If you have access to masses of oak galls or walnut husks, you can get much the same effect.
Oak is better with iron mordant, but that iron, it rots wool so ca' canny with it.
Copper on the other hand actually strengthens the fibres, but copper mordant needs careful handling, it's toxic in any strength. If you do want to use it, soak some offcuts of copper pipe in ammonia. That'll give you a beautiful ink blue mordant and that will help darken the colour of the tannin on the wool. You need to either soak the wet wool in the diluted copper mordant, or mix the mordant into your dyebath and get the wool in quick. Otherwise the mordant will help the tannin dye your dyebath and not your wool iimmc.
Lot of folks advocate salt but I don't find it does much apart from help berry dyes tbh, though it's needed for the commercial chrome (spit, hiss,
incredibly toxic stuff, causes feminization of the invertebrates at the bottom end of the food chain, just to give a brighter, sharper, colour!) dyes.
You do know we can buy green wool for £8 a metre ? I like recycling, I really do, but sometimes the logistics aren't the best option.
cheers,
Toddy