Non-receptive coloration and gravid coloration are the same. The only thing is that if she is carrying non-fertile eggs sometimes she will still mate with a male. She will act receptive though. It seems to depend on where she is in the cycle.
One more thing though...a gravid/non-receptive female can drop the dark background color when she cannot see a male. Sometimes she will keep the dark color when the owner or another female is around.