In reference to your night time question... Every vessel, regardless of size, if underway at night requires a "white" 360* light to be considered legal. Depending on size, your vessel may require port & starboard nav lights to be considered legal; so as for kayaks, you would not be "required" to outfit your boat with a red & green but you could do so if you wanted.
As a Coast Guard Veteran I feel compelled to mention day time visibility also. I know you guys love your camo but I can tell you first hand that camo and other similar "dark and/or nature" colors are incredibly difficult to see by other boaters in day or night; not to mention if you find yourself in need of assistance from search and rescue, then the very choice you made in the color of your kayak can make the difference in how quickly you find rescue. So if you have a boat like this, while you're outfitting it to increase your night time visibility you may want to think about day time also...and if you're purchasing a kayak/small boat you may want to re-think the color.
Oh, and a couple more things. Don't rely solely on your boat lights for visibility. Have a water proof, floatable flash light or spot light (like a divers light) close by and if you even think another boat is heading your way, do not wait until they get close to flash it. You'll be doing you and them a favor. One last thing: it's never a bad idea to keep a marine flare kit on board, you won't know it's there until you need it and then you'll be so glad you had it.
("Naked fishing is a bad idea")