PolyHarps are colored with skins that endeavor to have harmoniously related colors. It's not overwhelmingly successful, but it is better than nothing!
The largest circle on the color wheel represents a base color, the one all the other colors are related to. This is also the color of the background of the PolyHarp and the color seen in the list of patches.
The two smaller circles set the color of the string areas and chord buttons. Two contrasting colors are used in these cases. Touching and selecting with the double ringed circle will set both of these colors symmetrically. Touching the single circle will set just that color alone. You can similarly set the saturation semi independently or independently for these colors.
Around the edges are refinements in saturation and value for the selected colors.
The pairs of colors on the top left and right set the colors of the chord buttons. The top is the color of an unpressed button, the bottom is the color of a pressed button. You have two color choices for buttons (left and right).