Simply hook onto your toilet bowl and the flexible arm light will shine into your bowl no matter the size. You can choose a single color or have the colors fade into each other in a cycle. This is also great for kids learning how to use the bathroom! Colors include blue, teal, red, purple, indigo, green, yellow, amber, orange, white and more. Oh and there are five different levels of brightness so you can really customize to your taste.
Promising review: "I've had this device for a little while now and I absolutely love it! The toilet light is motion- and light-sensitive, which means that when there's too much light in the bathroom, the toilet light won't turn on, and if there's no light and no motion as well, the toilet light won't turn on. I ended up getting two of these toilet lights for both of my bathrooms. My guests, as well as I, love it. I give the product five stars for its low price, as well as all of the control and options it gives the user for changing the look of their toilet." —Sergio Rios
Get it from Amazon for $14.95+ (available in a pack of two and three).