what is the difference between light and dark, and bright and dull?

Answer 1

Light and dark refers to actual light...like the light produced from a lightbulb or the sun, while bright and dull would refer to intellegence or the brightness of a hue. Ex: white is bright, black is dull, the sun is light and the night is dark.

Answer 2

Light and dark relate to the amount of available light or contrast in a scene. Bright and dull relate to the reflectivity of a surface, e.g.
Lead is dull, silver is bright.