We perceive leaves as green because they are reflecting radiant energy of a wavelength that our eyes and brains “see” as the colour green. The other light energy wavelengths are being absorbed by the leaves.
At the extremes of colour reflection are the “colours” white (all colours combined) and black (no colours at all). A white object is reflecting nearly all of the light energy falling on it.
A black object is absorbing nearly all of the light energy falling on it.
Black collector plates and black cooking pots are most often used in solar heat collectors or cookers.
Light energy absorbed is re-radiated as lower wavelength heat radiation. An object of any temperature will radiate energy as electromagnetic radiation. The hotter an object is, the shorter the wavelengths of electromagnetic radiation that it emits (and the higher the energy per photon). The Sun radiates energy from its heated outer gases at about 5800 degrees Kelvin, and so emits energy peaking in the short wavelengths of our visible light range.
When an object is heated up on the Earth’s surface, by absorbing solar energy, it is never as hot as the sun. The electromagnetic radiation it emits will be of lower energy and longer wavelengths.
See also, as mentioned before : Electromagnetic Radiation, Temperature, Colour, Light