Light is produced when electrons vibrate, rapidly moving back and forth between various levels of energy that exist in the electrosphere of an atom.
For each jump, a photon is emitted, which is a monochromatic light of well-defined wavelength (color).
This results in the emission spectra, formed by streaks or colored bands, which even serve to identify the light-emitting atom. At high temperatures atoms with many electrons emit so many streaks that the spectrum becomes continuous and the simultaneous presence of all colors translates into white.
An object is white when it reflects all colors.
An object is black when it absorbs all colors.
An object is red when it reflects the color red and absorbs the other colors.