From my question on StackOverflow (CC BY-SA 3.0):

I’m plotting on top of an image in Matlab. Sometimes, I can’t see what’s being plotted because the color of the image underneath is too close to the color of the image at the same location. I could just always change the color of the plot (e.g. from ‘rx’ to ‘bx’), but that’s cumbersome.

Is it possible to plot the inverse color of what’s underneath so that the overlay is always visible?