Though I'm familiar with the material those tips are made from, generally with paint to match the covering you need to prime with a flat white primer before painting to get a good match. I've seen guys use red and gray primer and wonder why the color is darker than the covering. A good primer to use on plastic is the Tamyia flat white primer in the plastic model paints - it seems to be compatible with all the types of plastic used in plastic cars and planes. Use light mist coats since it's a lacquer based primer, but it covers great and leaves a fantastic base for paint. I use it exclusively now on my plastic models.

Hogflyer