It`s a Matter of Style!
The Traditional Norwegian knitting style usually has one base color and one pattern color, - like in the Selbu socks below.
Also, the contrast between black and white, or red and white, is a very popular combination of colors.
Sometimes, a second pattern color is used, like in the Marius sweater, - but the pattern colors are hardly ever used in the same row, but used separately, one at a time.
NORWEGIAN STYLE:
Other countries have THEIR special combinations of patterns and colors, too.