I use Faber-Castell watercolour pencils, and take the colour directly off the tip of the pencil, or - when I need a colour I don't have (I have a set of 10 pencils) - I create the colour on a piece of paper first and then take off the pigment with a slightly moist brush. The pigment of this particular brand of pencils is very vibrant and apparently very fade-resistant. The problem you will have with inkjet print-outs is that whenever you add water, the ink may spill... I tried using pastel chalk, but that didn't work out very nicely. The pigments stay 'dry' on the edges, and you need to brush off any excess pigment. Add to that the rather big size of pastel chalks, and you'll see that it won't work xD The last thing I tried was using the edges of pencils, but found that they, more often than not, will warp the paper.