-- Last Updated: Sep-25-12 6:53 PM EST --
there are two kinds of visibility:
visibility at night SOLAS tape as mentioned. Also a new product, NiteStripe, by a company called YakAttack - you can pick a black or red or yellow stripe to match or contrast w. your boat. It's visible at night when light hits it. Almost invisible by day if you go w. black tape on black boat.
Reflective deck weave is highly visible at night when light hits it. It comes in a mainly black weave w. about 1/3 white weave, so it will look good on an all black boat. I use it as full perimeter deck rigging on my otherwise totally jet black boat.
Visibility by day - brightly colored paddles, or stickers which reflect sunlight (NOT SOLAS). 3M makes it. Almost all boaters tell me they see the movement of paddles first and paddles the highest off the waterline.
Bright colored pfd and cap as mentioned.
I know a few kayakers who buy a hunter's orange mesh vest or highway safety worker's neon yellow vest and wear it over their pfds.
Don't paint the boat!