First add a hue/saturation adjustment layer to the image

Next add a channel mixer layer (remembering to select the 'monochrome' option)

You can adjust the channel mixer to get differing effects and then tweak the H/S layer settings to 'fine tune' adjustments.

Note how using an agressive expansion of the saturation with the Hue/Saturation layer and subsequent channel mixing has
emphasised some of the noise (mostly blue channel) from the original digital image. Pushing effects like this can give an Infra Red like look to the images (more info on IR in the links section).

Channel mixer layer was at R+60 G+30 B+10 (monochrome), Hue/sat layer was Hue+40 Sat +60