Share 'Should I give up this cover idea?'

Hey all, I am in the process of making up a dumpster diving zine, and thought of the following image for the cover, but since the rainbow makes the image, I'd have to get these professionally printed, and then with all that black it would be a waste of toner. Is the idea alright? Is it worth keeping? Should I come up with something else? Lemme know. Thanks!   Mike