int frame = 0;
int c = 0;
int vc = 10;
void setup() {
  textSize(10);
  frameRate(5);
}
void draw() {
  background(c);
  c = c + vc;
  if (c >= 255 || c < 0) {
    vc = -vc;
  }
  
  frame++;
  fill(255-c,c-255,0);
  text( "Frame #"+frame, 0, 10);
}