1) Twelve (12) dollar APC oil filler cap
2) Krylon "fusion" paint. This stuff stick to plastic with no primer - it's awesome stuff. Should live fine in the under hood heat as the covers do not get that hot. I did it myself in about 1/2 hour. Just remove and clean the covers, paint completely red, then paint the letters black using a brush. Dries to touch in 15 minutes, to handle in about an hour or less and fully cures by the next day.
The raised portions of the front calipers (fins and LOTUS), I blackened. The front caliper might also look nice as is but sealed so that it doesn't get stains in the pores. Or perhaps coated a solid color and then block sand the raised areas....