All of my kayaks have been red, yellow, or a combination of the two. My PFD is still red, as is my paddling jacket and dry suit. The only thing I use that isn't brightly colored is my werner paddle. I carry a C strobe in my pfd as well as a chemical light stick and whistle. On multiday trips I have a waterproof VHF radio within reach. When I teach for the school in Alaska I carry flares as well. But the biggest most visible object is my kayak, and I like it in a bright color. traditionally I have owned plastic kayaks, primarily because I can't afford a fiberglass boat. But also because I learned to paddle on very rocky beaches and a plastic kayak made sense. My current boat is plastic, but built like fiberglass, meaning it starts its life as two pieces and is joined together. I have a problem - in terms of visibility - with kayaks that are made of two pieces. A rotomolded kayak is one color top and bottom. For some reason, composite kayaks - be they thermoformed plastic like mine, fiberglass, or a kevlar layup - almost always have a colored deck, and a white hull. I would imagine it is to save money on materials, but someone more familiar with construction can correct me on that if I am wrong.
Here is my problem. Over turn your white hulled kayak. The white hull is now facing up. The bright colored deck is facing down into the water. If a search and rescue team or even a passing powerboat was looking for you, and your kayak was overturned it would look just like a white capped wave. If you are floating in the water, the majority of you is beneath the water as well, only your head and shoulders are above the water, so we are really relying on the kayak to be the visual that gets us noticed - forgetting about flares and strobes and the like. Now, I don't plan on ever being in a situation where I am out of my kayak, in the water, and unable to get back in, but Still I give it some thought. I also don't plan on getting into a car accident, but I have a car with airbags, and I wear a seat belt. This is why it is vitally important to think about these things. They call them accidents because we don't plan them.
As I have just learned that I can paint my kayak I am giving serious thought to painting a bright yellow stripe down the keel of my kayak. While I doubt I will ever be bobbing in the water next to my overturned kayak unable to get back into it, hoping someone will see me. I do think about the 'what ifs'. What if you were in that situation. What if a good day goes bad?