How to Mix Cobalt Blue
- 1). Thin the ultramarine blue in one mixing container, and thin the turquoise blue in another mixing container. If you use water-based paint, thin it with water. If you use another type of paint, use the appropriate thinner for the medium you use. Make it thin enough so it is easily mixed.
- 2). Add 3 parts ultramarine blue paint to the container, and add 1 part turquoise blue. Add the paint in any order, as long as you keep the ratio correct. If you mix the paint in a small batch, use teaspoons for measuring the colors. If you mix a large batch, use a cup. Stir the paint thoroughly. If it isn't light enough, mix in a little bit of turquoise blue.
- 3). Test the paint on a piece of paper. Let it dry thoroughly. Check the color. If it's too dark, add more turquoise blue. If it's too light, add a little more ultramarine blue.
Source...