Caulking type and brand?

It's not likely that you're going to find a good bedding compound caulk in colors other than white or black.  But if you do it right, white should be not be very noticeable.  I've used 3M 5200 and Locktite Marine Adhesive for mounting some stuff on our Pod and they work very well.  I used to use the 3M 5200 on sail boats and it was very effective in the harshest conditions for a very long time.  You will need to clean around the fixture to get rid of the excess caulk so you have a crisp edge of caulk around it's base of what you mounted. That way it hardly shows at all; just a thin white line.