It is an OK concept to play with, but it has become overused in general creative photography and as such it has become a less effective technique and more of a cliché. Being very artificial and unnatural, the question design-wise becomes: Why did you colour this element and not a different one, why the particular colour, and do the other pictorial elements fit together with the one that is colourized. Of course the ultimate question: Would the image not be more effective if it were completely and more naturally ALL in colour?
skieur