The image here is adding highlights to the characters in the same fashion as the shading. Really, it could have been a step that could have been skipped to keep the above cut edge image simple, but I just wanted that extra rim-light-like light source. Plus it allowed me to try a basic "knockout" technique with thor's lightening where the black lines were coloured yellow with a basic glow added to the layer.
To finish the image and "clean" up the file, a grey layer was added over the black channel; this is a mix of CMY and appears on all layers under the black line: basically in creates deep blacks in the black areas, eliminates the white areas missed under the black line and between the colours and if printed, will not expose errors if the prints don't line up exactly .( As the book explains :) )
Two things I need to consider when colouring my graphic novel: the characters will not be as brightly coloured as the avengers here, and also the environemtn light sources in the comic will be predominatley at night. So perhaps in my experiment I should change a light source, and try colur in a different method to suit a nighttime atmosphere? I've discovered early my lack of ability and patience with Brush inking, so maybe experiments with just colouring methods may be the order of the day? Maybe a different pen method (scratchier?) to contrast with the thick lines I inked the image with originally?