PImage foto;
color pickedColor = color(255, 255, 255);

void setup() {
  size(500, 230);
  background(255);
  
  cursor(CROSS);

  foto = loadImage("btk_teaser.jpg");
}

void draw() {
  image(foto, 0, 0);
  
  color currentColor = get(mouseX, mouseY);
  fill(currentColor);
  rect(450, 10, 40, 40);
  
  fill(pickedColor);
  rect(450, 60, 40, 40);
}

void mousePressed() {
  pickedColor = get(mouseX, mouseY);
}