I use shipping tape to coat mine. it does the same thing and still looks good.The tape is UV protected, so that means the paper underneath won't fade either. The tape protects against fading and weathering.
I print mine on colored paper to make the colors more vivid. I have an ink-jet printer (they suck), so anything you print out will be pixled. I just type out the black numbers in a 3"X3" text box on Microsoft Word and print it on colored paper.
I used a laser printer for mine but if you're using inkjet try using the photo setting and better paper...my highway sign magnets came out pretty sharp but you'll use up your ink a lot faster though.