RGB LED V1: Give RGB LED a random color at start.
RGB LED V2: RGB LED's color changes every 0.5 second.
RGB LED V2.5: Extract `setLed(int ledPin, int color)` function.

Eliminates duplicated code inside function `setup` and function `loop`.
RGB LED V3.1: Create two arrays to hold LEDs' current and target values.

Give random color values to LED when starting and store it in currentValues.
Generate another set of random colors to be targetValues.
RGB LED V3.2: Add decomposed steps of transition in loop.