Is there a trim you can use as a border between paint colors?

SO I painted my son's room two different colors and I used tape to get even lines. It came out ';pretty'; even but it would look great if there was like a thin black (or other color) border. I dont want a traditional wallpaper type border. I am thinking of something that looks like a 1/2 inch electric tape. Just a simple color trim. Anyone heard of anything like this?Is there a trim you can use as a border between paint colors?
Wood Molding. It comes in 1/2 ';up to 6';. Like chair rail. Paint it black before you put it up. Tack it up with finish nails. I hope this helped.