Describe two ways to decrease the intensity of red?

If the question is how to decrease the intensity of the color red in wet media like paint one method is to use a small amount of the opposite color (in this case green) to decrease the intensity. Depending on the red, cadimium can mix with earth tones, but a red like alizarion will tone down with some cool yellow or blue. For the most part it really depends on the type of media and the type of pigments. Having a working knowledge of the color wheel and transparent and opaque pigments, along with experimentation is the best way to find the right mix.