Brake or silicon.
Won't wash out when wash the car etc. Doesn't "melt" and stain anything drips on.
Likely have other problems... Roller stop have plastic bearing that wears out and makes noise. Lube only helps short term a best when this happens.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave