I got a quart of 'mis-mixed' from HD as well. I needed a more 'earthy' color, so I went up to the mixing table and asked them to squirt some more dark brown in it. They said they normally didn't do that because some folks have deliberately mis-mixed paint, returned it, then came back to repurchase at the lower price.
I told them I was a model railroader and needed to paint the terrain a 'dirt' color, so the manager there said 'OK'. It's still not very dark (it was some beige color to begin with). I went to Michaels and bought a tube of Dark Sienna to see if I can darken it further. I may end up mixing it bit by bit....
Kennedy