A product that many people may not be aware of is auto cycling LEDs. These LEDs have a build in IC that will cycle the LED between multiple colors. Digi-Key has a selection of RGB LEDs that will cycle without a microcontroller. Another feather of these LEDs is that they will accept a range of voltage and the IC eliminates the need for a current limiting resistor.
Sparkfun offers this diagram in their data sheet.
While you can see a slight internal change over a standard LED it is hard to tell the difference without looking closely.
Another neat group of LED to look at for your next project is Flashing LEDs that will automatically flash / blink without a micro.