How can one make chromatic light using LED. like razer deathadder chroma does
Such nice fluid transitions
For what can I use infrared LED light (scrapped from razer deathadder)
Simplest option: get an LED which does this automatically. One component, done. They aren't even expensive.
More complex option: get an RGB led, drive R/G/B suitably. You can use a microcontroller to produce the dimming patterns.