The term 'not so bright' can be described by the crossword solutions of obtuser (7 letters), dimmed (6 letters), paler (5 letters), and DIM (3 letters). Obtuser means lacking sharpness or quickness of mind, dimmed means made less bright, paler means having a reduced intensity of color, and DIM means not bright or vivid. All of these words describe something that is not as bright or vivid as it could be.