I'm with Guthwine on this, the grey ones look fine while the brown ones, while painted to the same standard, look a little bland because they blend into the brown of the chariot. That said, they look fine to me, I'd be very happy to play with/against them.
What really makes the crew stand out so nicely is the bright clean colours you've chosen and in my (minimal) experience of painting WM it seems that daring (bright) colour choices are often rewarded in a way that isn't so true at 28mm.