My car has pin stripes painted on it ( like that when I bought it) and orginally had pin stripe tape separating the two colours but i ripped it off because it looked cr-ap.

I would like to separate the two colours with a black line and don't want to go back to tape as it always has to be replaced.

Any ideas. Is there like a paint pen that will allow me to do straight lines.

how about two strips of that "paint friendly" masking tape (i think its the blue one) down the side of the car and then paint the gap in between them?

why dont you go get a new strips? those rubber with chrome strips on the centre or all around, they got this strong adhesive and you can buy them by metres or they can install it for you.

airbrush artists could help you
or a specialist who does truck pin stripes
if you are after some kind of "paint pen" try a sign writer...

only suggestions. I would probably just stick with vinyl, like used on boats and lots of car graphics... could even get a really thin hod rod style of flame in a colourflip vinyl to seperate the two colours...