Originally Posted by giorgio130
... Otherwise if they're monochrome leds it would be quite impossible...
Moreover, the technology used to diffuse light should be quite sensible to the wavelength of the radiation, so it's possible it would not work with a different color.
Energy efficient white LEDs as used in this application are really just blue LEDs with a white phosphor coating. Replacing them would require SMT rework skills (which I have), and replacement LEDs in your choice of color that have the same component footprint and power requirements. Different colors have different requirements.
Tri-color LEDs require much more complex driving circuitry, so it is very unlikely that they would be used in this application.
White light is fairly full spectrum, so filtered narrow spectrum (single color) LEDs would work as well as white for their comparative "diffusion" (or light guide propagation) properties in the Paperwhite kindle.