Colours directly opposite to each other in a colour wheel and appears opposite in character are called complementary colours.
- rose versus aquamarine
- violet vs chartreuse
You can see them in this RGB wheel.
In a subtractive model (ink, paint, printing), there are three opponent channels that creates a color closed to black (brown).
You can see them visually in this ryb star:
Colors that are directly opposite each other on the colour wheel.
A colour and the two colors adjacent to it’s direct complement.