You can serve different combinations of bands from a single set of images by creating a new Express Server catalog for each band or set of three bands that you would like to serve. There is no need to copy the source imagery to a new folder. Simply create a new, uniquely named catalog from the same folder (see Adding a Catalog) and map the bands as desired for each one (see Mapping Bands).
NOTE: You can map bands for MG4, NITF, and JPEG 2000 images only.