Conventional colors of atoms.

Are atoms colored? Not at all! Substances are colored and their color is due to molecules which they are formed of. Conventional colors of atoms are chosen only on pratical reasons! Let's take f.i. the molecule of urea :

It contains 2 atoms of nitrogen (N), 4 atoms of hydrogen (H), 1 atom of carbon (C) et 1 atome of oxygen(O). If atoms had really their conventional colors, urea would be brown, a mixture of blu, red and black. Urea is a white solid in reality!