Many will remember from school lessons of drawing that purple is a secondary color, so to get it you can use two primary colors red and blue. Take a brush and some red paint and put it on the palette. Then, do not forget to carefully rinse the brush in the water, grab the blue paint. Paint need to take in about equal proportions, only slightly modifying them, or if one of the colors will be much more the color will vary from dark purple to crimson.
If you want to get light purple, pink take dye, put it on the palette, and then add blue and mix thoroughly. Apply a few strokes on the canvas, perhaps that this shade suits you perfectly.
To get the purple color, you can go the other way. Take purple paint and mix it with white, not forgetting to rinse the brush, so as not to spoil the entire tube. Varying the amount of white paint, you can get the purple color of varying intensity.
In principle, any color belonging to the blue color of the pigments when mixed with cool red gives purple. If you are seriously engaged in painting, certainly you have not only the packaging gouache of six colors. Therefore, to obtain you necessary purple, mix red cobalt, ultramarine, cerulean blue, phthalocyanine blue. Adding to the palette a little white paint and mix thoroughly, you can lighten your final color.
Mix the black paint with any cool red color. This may be a phthalocyanine or alizarin red. In the result you will get muted purple color. It will be more dull and not as chromatic as the pure pigment, but nevertheless, you will get exactly purple.