I've been doing some research ever since I purchased my kayak and so many people have said I should have chosen yellow over blue. That is the colour of my deck, and once it is covered by equipment, very little blue is visible. Besides, in my research I learnt that having a bright yellow deck can be really hard on the eyes in sunlight. Having a white hull on a 14 foot boat isn't good either, when it is tipped over it may be confused with white caps. Then there is the school of thought that any colour of kayak is fine and it is more important that the person paddling should be making themselves visible.
On this note, I learnt orange is the best colour followed by yellow and then red. Even red gets a bad rap in that it can look black in shadows. One colour of kayak I did notice when I was shopping around was robin egg blue which I really liked. Interestly enough this colour is actually great for a boat. Why? Because robin egg blue isn't a colour seen in nature except as robin's eggs so something that is kayak sized is going to look out of place on the water and attract attention. Another colour that is good for a kayak is lime green and I do have to say I did notice the demo in this colour sure drew my attention when it was out on the water during Paddlefest in Ladysmith.
I have an orange PFD, throw bag with a bright yellow rope and orange paddle float. My main paddle is white and my spare paddle is black with green reflective tape. I should be wearing a bright orange or yellow or red hat; I own a red ball cap which I intend on wearing during the summer months. I wear a bright pink rain anorak during the summer months and I'm sure it can been seen from a long way off.
Another thing about colour, if you are planning on getting close to nature forget it if you have a yellow kayak. It is the darker colours that don't upset birds or other sea life. Which is maybe why I've gotten so close to ducks with their young and seals like to check out my boat.
If I ever go night kayaking I should put more reflective tape on my paddles and gear. Carrying glow sticks is recommended or lights. Much the same advice if you were cycling at night applies to kayaking at night.
The whole issue of being visible had me thinking -- visible for what? So far I haven't paddled alone and we've always let someone know where we are going, and phoned in on one of the three cells phones we carry to let that someone know we are ashore. I prefer to paddle with a few friends and don't like to go too far from shore.
Still, it doesn't hurt to be cautious and learn all one can about safety. Two web sites I found some of my information on were: www.roguepaddler.com and www.paddlingnet.com
Enjoy kayaking and stay safe.