Depends on the specific sign which you failed to list.
(in the US) White with black letter/numerals.
manditory instruction signs
Red and white.
Regulate
Those signs are called prohibition signs, and whatever is pictured behind the crossed out red circle is forbidden. Some examples: safetysignsservice.com.au/signs/prohibition-signs
stop signs appear red because some people cant really see colors, so the red is bright so them people can see the brightness :D
Red, Yellow, Green, Orange, & White.
They are signs of white supremacy
blue = loyalty red = bravery white = courage
Signs which denote Interstate Highways are red, white, and blue.
B. regulate