A landscape by Shusei,
Muromachi period, early 15th c., Japan,
ink and watercolour on paper.
The sure and delicate touch of a true artist may brush across our minds and make us appreciate subtle variants of tint and shade.
Yesterday, PBW posted some helpful guides to blending pigments and palette to avoid superficial bland and blah.
I highly recommend reading it.
So, ask yourself, for example:
(1) Do most of your characters fall in the same age group?
(2 Do many of them have sound-alike names, such as John, James and Jim?
(3) Do they all belong to the same ethnic group?
(4) Do they provide ethical variety as opposed to a straight good vs. bad alignment?
Good questions that need good reasons for choice.