I had one patch that stuck out like a sore thumb in half the blocks - I started the brown section with a fabric that should have gone with the tans.
I recolored that patch on all fifty blocks with Fabrico markers - the brown marker by itself turned out too red, so I used a layer of pine green first, to tone down the reddish look, then put espresso brown over the green. Some of them got several layers.
I used a really light touch, but you can be as bold with these markers as you want to.