Krylon spray or lacquer dip in white under the entire length of the cap, then whatever color spray or dip over that you want with the same type of paint.
Crest with Testor's (some will need thinning) then water-based poly dip (over entire cap/cresting for protection. Get decent brushes (natural bristles) you'll be glad you did. Not sure on TN stuff, but Bohning is good stuff, although pricey and stinky. Water-based paints I've tried from Whispering Wind were nice.
Good luck and have fun, those Spinrites look slick.