I'm thinking it's some old paint as Testors Floquil brand does not have an R/C line.
Check the bottles, are they acrylic, enamel or lacquer?
If memory serves correct, I think that color is from Floquil's military line before Testors aquired the brand name. I'd play it safe and test the paint on a piece of scrap polystyrene (model plastic) to see if it effects it.
Sorry I couldn't really be of much help.