Plan ahead - a simple jar of Vasoline provides pretty good waterproofing if you don't have access to a transparent grease like Michlin. Smear around the headtube, seat-tube,BB and wheel bearings. Be generous. Take the excess off with a rag when you get where you're going. Rubber seat covers are available for riding in the rain with or without you on the seat.

I'd recommend against using a colored grease as it can actually stain the paint.