Can You Apply A Color Palette to a Custom Group?

In an RTC Project, we have a query that identifies members throughout the U.S.  For some of the widgets on the dashboard, we are grouping the members from each state together (instead of all of the cities and states) using "Custom Groups".  That part works great.  What we want to do now though is apply a special color to each of the "Custom Groups" (i.e. "States").  But when we select "Color Palette" it only allows us to apply a color to the initial list of City, State and not the new Custom "State" Groups.  Is there a way to apply a Color Palette to the Custom Group?