No. Aperture tries to maintain a neutral working environment. When Leopard first came out, and there was no option for an opaque menubar, Aperture overrode the transparent menubar when the app was active. It was a bit annoying to have it change (though I personally hate a transparent menubar anyway), but I could definitely see the reason. You don't want a lot of distracting colors in your image workspace. Thankfully, Apple chose to make the opaque menubar system wide.
Anyway, you'll notice all the tool buttons around the browser and viewer are grayscale. When you turn off the inspector and toolbar, everything except the image is in grayscale.