Control the colours of your RGB LED with Processing.

Use the attached RGB Processing file.

Furthermore, if you haven't done it yet, you have to download the Standard Firmata program library to prepare Processing for Arduino. Open the Processing Sketchbook folder. (You will find the path if you go to Processing and click on Processing > File> Preferences.) If the Sketchbook folder still hasn't got a libraries folder, create one yourself. Pay attention to the spelling: libraries. Then copy the Firmata program library into the folder. The library will be automatically loaded when you run Processing.

Start up the program Sketch > Run. Selecting the port The Processing window has a black output area at the bottom. When the program is launched, all connected devices are displayed. Remember the number that appears at the beginning (e.g.: 0) of the line referring to the Arduino. On a computer running Windows, it is usually the last entry (eg COM3), on a Mac it is the first or the last entry (z.B. dev/tty/usbmodemfa141). Close the program, and insert the number into the program code line: myArduino = new Arduino(this, Arduino.list()[0], 57600);