This page shows you other colors you can add to your scheme. For the most part you can choose any color you like on this page, as long as you still use colors with all the 4 different hues in the basic scheme.
But remember that the less number of colors you choose, the easier it is to make soomthing which looks good.
Each line below shows an example of a complete color scheme. Your basic colors are combined with different shades, lights and neutral colors.