I was about to mar the fruit with grey highlights, when the instructor intercepted brush and canvas just in time to point out the shadows were actually a cool blue/purple hue. While he was at it, he added green to the aubergene pointed out its reflection in the bottle, and then drilled me on primary, tertiary, intrinsic and focal colours.
I couldn't believe my eyes.
I'm thinking now of Berkeley's theory of subjective idealism, wherein an individual can only realise sensations and objects directly, and not in abstract terms. To be is to be perceived.
On the flip side, this doesn't mean that what is not perceived (at least by my amateur eye) cannot be. Apparantly the colours exist, but are only perceived when pointed out to me. Alas, my head spins, my eyes ache and my clothes are covered in splotches of green and blue and burnt sienna that never existed until I put them there.