I have the following scenario:
This is a color picker for a software we're developing. Basically we have different Groups for Items and Items are displayed as boxes in a grid with a given color scheme that can be customized through the following interface.

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Before today we didn't have many groups or categories to put the items on, but the problem is that the number of groups for a specific instance of this interface has grown, and we just cannot keep adding radio boxes or tabs to filter the items.
I thought about having a collapsible list with the table inside, or even an accordion to hide inactive categories, but the problem with the accordion is that with a lot of groups it's just useless.
I also suggested, having a default color scheme, and then only aggregating changes, but the problem with this approach is that you might have adjacent item boxes together that might look similar if you're not able to compare them from the list.
Someone else suggested having the groups in a dropbox... but you're the experts... so I rather hear it from you guys! :)
What would be the best way to present this color picker.



