The RGB illumination system is obtained by rotating all the colors of the spectrum by combining the various light elements together from red, green and blue light respectively. The tri-colored LED is used to get this spectrum. This spectrum is obtained by implementing Hue Saturation Intensity (HSI) algorithm which allows the intensity and brightness level of the spectrum can be controlled mathematically. The HSI algorithm is implemented on PIC18F microcontroller and designing the interface circuit to control the tri-colored LED.