2025RNAAS...9..168R

Brown dwarfs (BDs) are in fact not brown. Their name comes from their falling between red low-mass stars and dim dark giant planets in size. But what is the actual color of a BD? We can also ask this question for exoplanets: is Earth the only pale blue dot in the Universe? In this work we investigate such questions by simulating emission spectra of both cloudy and cloudless BDs and exoplanets, and converting them into colors detectable by the human eye. We find that the resulting hue depends greatly on the type of clouds in the atmosphere. Moreover, cloudy BDs turn out to be blue for the T-types and purple for the L-types. Young massive exoplanets should follow the same sequence of colors but with a delay of the L-T transition. Our results can serve both for outreach purposes and for the interpretation of observed reflectivity spectra.