Why does a molecule have the color it has:

An atom has a number of shells containing electrons.
They can only have an exact number of electrons per shell.

U-238 has 238 electrons, arranged in multiple shells.
Each shell is 1 quantum distance further from the next.
The gap between the shells gives an interference pattern
when light hits them (photons going through an atom).

Think about the slit interference patterns produced when
photons pass through a narrow slit.

It is like the green feathers of a hummingbirds' chest -
they are not green at all, but clear with many slits to
allow the photons to produce a green color - due to
interference patterns.