Arizoni - you may recall a PM discussion between us about this. I am thinking about highlighting my engine in a similar fashion. My bike has the same plastic starter cover, but rather than the "Royal Enfield" text, my engine covers have the cast winged logo with "RE" letters that match the starter cover's.
My tappet cover is the same as yours, and yes, I was thinking about coloring it to match the rest, but the corners of the recessed lettering are crammed with white gunk - it looks like some kind of wax or polish that is a pain to clean out without a metal scraping tool. I figured taking the cover right off would make it easier to clean, and easier to re-paint at my desk rather than crouched in my dark garage...