Aside from skiing down Mount Washington, or the back country in Wyoming, there is nothing like paddling on a beautiful summer evening. But, as someone who has extensive experience with night operations doing routine patrols, search and rescue, and relaxing in my kayak, you need to be extra vigilant and prepared for anything!
As Oliver stated Navigation Rules (federal law) requires “lighted lantern that can show a white light in time to prevent a collision” from sunset to sunrise. There is criminal law and the law of common sense. Criminal law says you have to have a life jacket onboard your vessel, while the law of common sense says you wear that life jacket; the same goes for lighting. Although the law permits a flashlight—and if you are paddling in a small harbor with a no wake zone this may be sufficient—if I am in Long Island Sound, or even a large lake, I want to look like a Light House. While close to shore (where most paddling occurs) it is extremely difficult to distinguish vessel lights from the shoreline lights, and a single white light is almost useless. Red and green side lights defiantly attract more attention, even if they are glow sticks. I display battery powered sidelights, an all-around white light behind me and a strong headlamp. With a small 18” chop even those are visible only 50% of the time. Another great help—especially if we are searching for you—is Retro-Reflective material: I have it on my paddles, life jacket, top and bottom of the boat, and all accessories; even my deck lines are reflective. It may seem like overkill, but what is your life worth? Out there you are like a water bug in a trout pond.
Safe Boating!