A color test is a test that can be applied to an isotopic class or any projection thereof to determine if a "color" value can be applied to each arc of a projection while following these rules:
Rule 1: All colors in the color test are used.
Rule 2: Either Property A or Property B holds true.
Property A: The colors of the arcs that meet at a crossing are all the same.
Property B: The colors of the arcs that meet at a crossing are all different and follow a pattern defined by the specific color test.
It is important to note that the results of a color test are not affected by any isotopy.
A specific and popular color test is tricolorability. It simply tests for the ability to color a knot with the above rules and only three colors.