Hello everyone. The title of my question may look a bit silly, but I think it is quite interesting. Before a couple of days, my aunt told me that she found a paint? for her nails, which had the following feature: her nails would have a specific color when she was in her house and a different one when she went out of it. That was a bit surprising and at first I could not figure out why would this even be possible. I assumed that, since the wavelength spectra of the photons that exist out of our houses is the same with the one, in them. Then I "stepped" on WIEN'S law and wondered if it has to do with the different temperature between inside and outside the house.