First, mix red and yellow together in equal parts to make orange. Mix one-fourth part orange with one part ultramarine blue. Since orange is the complementary color to blue, it will darken blue’s hue. If the color is too dark, add more blue. If it is too light, add more orange.
A regular true blue mixed with a little black can make navy blue. Cobalt blue, mixed with a touch of purple also makes navy blue. If you want a very deep, but bright navy blue, mix regular or true blue, with a touch of black and a tiny touch of purple.