Arduino Task

Arduino End:
Recieve a string of numbers, comma separated (e.g. 255,128,20) and store these in 3 separate integer variables
 
Raspberry Pi End:
Send a set of numbers commas separated to the Arduino via i2c
Extension: using the node red dashboard, get 3 numbers from the user on the dashboard and send the signal via a button on the dashboard

https://docs.arduino.cc/language-reference/en/functions/communication/wire/