Is there a data plate on the sill of the drivers door? If yes it might have the colour codes listed on it. It could be black with a silver border. This is your best bet.
And just to be sure, those are painted and not striping (stickers)?
Google is your friend, I found the following
Paint Chips 1986 Ford Truck
However, using the page below it appears that there was no purple in 1986
Purple Ford Econolines at PaintRef.com
So this was
1) an upfitters colour choice, and not factory paint
2) it wasn't called "purple" by Ford in 1986. I know that's strange to understand, but it's how auto manufacturers work.
3) that website is missing data or full of it