If only the PL polyurethane roof flashing came in a gray color. I called tech support if this came in a gray color. The answer was no. There is a concrete crack and masonry gray, but it has a some sort of grit mixed in with it.
IMHO, I would use a blue painters tape around the edges before applying the caulking. Then use a rubber scraper used for caulking edges in the bathroom and kitchen applications. After excess caulking is removed and cured a little, remove the painters tape for a cleaner application.
1947 Curtis Wright
1958 Traveler 18'