function to control an rgb led

Hi, forgive me for my bad english.

I'm trying to control a simple RGB led. My actual code is working, but I'd make it more ... fluid:

function fade(led) {
  for (i=0; i<=255; i++) {
    digitalWrite(led, i);
  }
}

I call this funtion with the pin number of the led to control. But I'd like an async function that can run a "sequence" of colours while checking in the same time the state of a push button (to turn on/off).

I'm really not a developper, but I know that someone could help me to finish my little led lamp project for my daughter :)