Kirchhoff's law of thermal radiation says that:
For a body of any arbitrary material, emitting and absorbing thermal electromagnetic radiation at every wavelength in thermodynamic equilibrium, the ratio of its emissive power to its dimensionless coefficient of absorption is equal to a universal function only of radiative wavelength and temperature, the perfect black-body emissive power.
I can imagine why dark objects have higher absorption of electromagnetic radiation: The darker the object is the less radiation it reflects back. An ideal black body would absorb all the incident electromagnetic radiation.
Is there a similarly simple and intuitive explanation of why dark objects emit thermal electromagnetic radiation faster that light objects and why is the Kirchhoff's law valid? For me it is not intuitive at all and I was not able to find any simple explanation.