Not sure if this is a Physics question, but...
Why is it easier for inks to show up on white paper than on black?
You can get "special" inks which print solidly on top of black surfaces, but your common stock will make black paper look as if it's merely tinted, whereas the colours show up boldly on white.
It's confusing to me for two reasons.
Firstly, human sense organs respond approximately logarithmically. As in, a drop in light intensity from 100W to 99W will be less noticeable than a drop from 10W to 9W. This would lead me to predict, since colours are defined by the wavelengths they subtract from a white source, that the lower baseline quantity of light from a black surface would make the coloured inks on top of it seem bolder against the background than the same intensity-differential-per-wavelength against a higher intensity background.
Secondly, if you start with an RGB colour which is (100,100,200) units (i.e. blue-grey) and then add intensity uniformly to, say, (1100,1100,1200) units, then the proportions are closer to unity, i.e. the colour desaturates. If the explanation for my question was "the ink allows some white light through which bounces off the paper and returns, making the colour brighter", then I would expect inks to desaturate when you shine brighter lights on them. But this doesn't happen.