void setup() {
  size(500, 500);
  background(255, 0, 0);
}

void draw() {
  background(255, 0, 0);
  fill(0, 0, 255);
  ellipse(250, 250, 50, 50);
  color myColor = get(mouseX, mouseY);


  if (red(myColor) == 255 && green(myColor) == 0 && blue(myColor) == 0) {
    println("it's red");
  } else if (red(myColor) == 0 && green(myColor) == 0 && blue(myColor) == 255) {
    println("it's blue");
  } else {
    println("it's something else");
  }
}