false color highlights seem to be an issue frequently, so here’s some quick faq about it. alexandre, please excuse all the outward references ;)
why are my highlights magenta?
that’s how the sensor works. it collects a couple of photons, at some point it fills up and rejects to deliver any more useful information past this point. unfortunately that doesn’t happen at the same time for all color channels.
how does the sensor work?
usually digital cameras come with a color filter array (CFA) of absorptive filters in front of an array of CCD or CMOS sensor which collect electrons proportional to the incoming photons according to the photoelectric effect.
This is a companion discussion topic for the original entry at https://www.darktable.org/2012/07/magenta-highlights/