you might use any epoxy with some red nail-enamel added - however I've never tried this myself on big surfaces or to repair scratches.
you also might dissolve some red transparent plexi from a dead watch using a chemical solvent called Toluene
http://en.wikipedia.org/wiki/Toluene
throw in small parts (of most types) of plastic into a very small glass container with lid and fill it with toluene (apply less than more). after a day or two and periodic mix, the plastic will be completely dissolved into a plastic semi-liquid substance. apply this "glue" onto parts made of the same plastic. after the solvent has evaporated, the only thing that will remain is the plastic itself which you can afterwards file down to shape and polish to shine.
as a kid I used to assemble plastic cars and airplane model-kits and toluene was the best solvent used to make real plastic glue using the plastic leftovers after the car parts were removed. the "glue" has the same color so most often the models didn't require paint to cover the stitches.