Normally, we tend to use saturation and hue to improve colours (all or individual Red, Green Blue channel(s)). However, it is possible to use the "Channel Mixer" option to reach some stunning result - with a bit of trial and error experimentation.
Here is a picture posted earlier - Autumn
http://forum.timway.com/f/thread-158426-1-2.html
This is the same photo - with channel mixer (for red channel red +120% green -20%, blue -20%, green channel green +120% red -20% blue -20% etc). A bit exaggerated may be (the colours).
A bit of usual adjustment of of level, shadow/highlight, and curves to to compensate for the distributuion of brightness (histogram). This bit needs a little explanation if you feel I am using a foreign language - but you can igonre this for this moment if you want - it will not affect the colour enrichment.
As always, you need to experiment to obtain result that pleases you (and/or others) and to ensure that these colours are actually printable. Printers do not have as wide a range of colours as monitors and hence it is always worhtwhile to check that before printing (especially large prints).
