[NTG-context] full page images on fixed pages

In my current book project, I need to set images on fixed pages (because only a few pages get printed in color), and full-page, i.e. bleeding 3mm. What’s the best way to achieve each? The only way for full-page images that I know of, is via layer/ background, but I find it difficult to activate and deactivate that at the right pages. Greetlings, Hraban --- http://www.fiee.net/texnique/ http://wiki.contextgarden.net https://www.cacert.org (I'm an assurer)