why do these gases absorb specific colors of light?

For example, oxygen gas snatched up some of the dark red light,and sodium grabbed two bands of yellow.But why do these gases absorb specific colors of light?This is where we enter the quantum realm.Every atom and molecule has a set number of possible energy levels for its electrons.To shift its electrons from the ground state to a higher level,a molecule needs to gain a certain amount of energy.No more, no less.It gets that energy from light,which comes in more energy levels than you could count.