3 is one too many colors seen on the outside.
Ever seen a Mod Top or Floral Top car?
How many colors in the top alone?
Multiple colors are cool.
Mod tops have one pattern over the entire top.
I don't think multiple color are horrible. Just when top and stripe match it's more visually pleasing.
V21 challenger with black hood and white stripe just don't flow as well. White and black are considered neutral. But you don't often see a cream painted car with red painted top and green stripe.
The factory suggested color combinations set by the factory stylists take in account 1) interior and 2) exterior colors for 3) stripe choices. It also considers 3 colors for 2-tone combinations making sure at the very least one exterior color matches the interior color.