Good stuff so far. I'm presuming that the colour which looks brown is the Dark Earth. If that's the case then the Mid Stone definitely looks very green, even allowing for light and colour balance - the colours in the background of the shot look OK, so I'm thinking that paint is way off.
Unless there's something in the paint, or the lighting set-up, causing anomolous reflection, which is a situation where a photogrpahic film, or sensor, records closer to an actual colour, rather than how the eye would perceive it. It used to happen a lot in wedding photography, where a man's black suit would appear blue, or reddish brown !
Is there by any chance a fluoresecent lamp in the room?