Not only that, but the cobra head of the ship is lavender in one shot and green in another.
Looks like the on-set lighting was overwhelming whatever colors the model was painted with.
By-the-by, I recall having a Star Trek: The Magazine issue sitting around somewhere where Jeffries talks about the D7 design and construction, and I recall he mentions it being painted in two tones of greeny-gray, inspired by sharkskin. Anybody else remember that?