Nice Pattern W2812 to fiddle with

Hello Friend of the big Arduino
Does someone know code samples to fiddle with RGB Leds

ats3788:
Hello Friend of the big Arduino
Does someone know code samples to fiddle with RGB Leds

The Adafruit NeoPixel library has examples for WS28xx LEDs.

How to install

What kind of RGB LEDs? There are two main types. There are "dumb" LEDs which need 3 Arduino pwm pins to control them, and there are "smart" ones sometimes referred to as "NeoPixels" where many leds in a chain can be controlled with a single Arduino digital pin.

I have an P9813 controller with the right Led string and also a Led string with W2812 Controller

ats3788:
P9813... W2812

Both "smart"/"NeoPixel" type LEDs. As suggested, look at the AdaFruit NeoPixel library examples and also the FastLED library examples.