One of the hottest trends in stamping right now is coloring your images with Copic Markers.
Copics are alcohol markers that come in four different styles, with different replaceable tips in up to 322 different colors that are non-toxic and dry acid free. There is even a separate air brushing system. They are wonderful for blending and shading your stamped images. The Copic website has a very informative pdf file about using Copic markers with your stamps.
And check out Christine at Scraptime who has a really great beginners video for getting started coloring with Copic markers.
-Heather