@goldee do it in scriptnode. set up a new filter for each band (check on here as to which filters are working properly there was a thread from @aaronventure on it), set each filter to the same external buffer display. Then on your UI set up a FilterDisplay floating tile for each band / filter and change the colours (via LAF if you want gradients).
The nodes you can do with the snippet above and a draggableFilterPanel floating tile...