Elaborating on darsben's reply, there are two "seals" on an RV window. The primary seal is between the frame and the sidewall, usually butyl tape. The visible external sealant around the edges is an assist only, intended to help water run away rather than possibly collect in a gap and work its way through the primary sealant. It is generally along the top edge and part way down the sides, but not on the bottom (where you want any water to fall away). Most manufacturers use a clear silicone sealant for that, but silicone is not paintable. You can use any sealant that is suitable for metal or glass surfaces. Geocel Proflex RV is one excellent alternative that is paintable, but you can find a variety of others at any hardware store or home center.