The colour black does not, by itself, “make things get warmer”, and in fact it sometimes makes them get colder. But it does increase the rate at which they absorb energy from visible light and so increases the rate at which they will get warmed up by sunlight. The other side of the coin, however, is that if the blackness of an object extends into the infrared part of the spectrum then the object will get cold more quickly if exposed on a clear night. This is because the way physics works is that there is a universal connection between the rates at which an object absorbs and emits radiation at any given frequency, but the frequency distribution that it emits depends on its temperature. (The only reason we don’t normally see more light from a black body than a white one is that what we see from the white is not emission but reflection, and when the object is hot enough to emit visible radiation then in fact the “black” one will glow brighter.)