Study in white?

Ten years ago at the Royal Academy's 'Masters of Colour' exhibition I stood in front of 'Portrait of a Young Woman in White' trying to do as the caption asked and work out what colours Renoir had used to create white. Since then I haven't known what white, or any other colour, is.

Sometimes I use Photoshop's eyedropper tool to sample pixels in a picture and I'm usually surprised. Paintings of lace are particularly interesting. There is almost no white in this blip.

White
Pale

I intended to link yesterday to a photo I took at King's Cross but nothing would upload to my blipfolio and today is no better :( Are other people having problems?