I've only seen black or gray. But I have painted them successfully using plain old ordinary spray paint, and I know others have successfully used plastidip. So it probably wouldn't be hard to paint them red.
I would not paint dreads with spray paint, as they flex too much which would cause the paint to crack possibly, but you can paint them just like a latex mask with acrylics or inks.
i have used both and it is a easy process.
I used regular acrylic paint on a few of mine. It seemed to work just fine, but I ended up going through a lot of paint. Since I was on a budget, I scrapped that idea. They turn out nice, though.