When you mix green paint or dye with purple, you get a dark greenish-brown colour. Color mixing means putting together two or more colours to make a new colour.
There are two different ways to mix colours: adding and taking away. In each of these ways, the primary colours are different.
Yellow, magenta, and cyan are the three subtractive primary colours that can be used to mix colours for things like paint, dye, and ink. When you mix these three colours together, you get black.
Red, green, and blue are the three primary colours that can be used to mix light or illumination. When you mix these colours together, you get the colour white. When you mix red and blue, you get magenta. When you mix red and green, you get yellow, and when you mix blue and green, you get cyan.