Why not buy decal paper (clear or white background) and print on it using your color printer? It is a lot easier and a lot less destructive to your printer than inserting metal or plastic sheets. I have had success creating colored letters and images on clear decal paper in my color jet printer and then fixing them with a spray on decal sealer. I then cut out the decals and affix them to what ever surface I choose.

Decal paper and sealer can be purchased from most hobby shops (online or brick & mortar).