int farbe,farbe2;

void setup() {
  size(400,400);
  fill(200);
  farbe=1;
  farbe2=1;
  ellipseMode(CENTER_DIAMETER);
}

void loop() {
  if(farbe==1) fill(200,0,0);
  else fill(0,200,0);
  rect(200,200, 100,100);
  
  if(farbe2==1) fill(0,100,200);
  else fill(255,0,0);
  ellipse(100,100, 80,80);
}

void mousePressed() {
  if(mouseOverRect(mouseX,mouseY, 200,200, 300,300)) {
    if(farbe==1) farbe=0;
    else farbe=1;
  }
 
  if(mouseOverCircle(mouseX,mouseY, 100,100, 40)) {
    if(farbe2==1) farbe2=0;
    else farbe2=1;
  }
}

boolean mouseOverRect(float px,float py,float x1,float y1,
  float x2,float y2) {
    if(px>x1 && px<x2 && py>y1 && py<y2) return true;
    else return false;
  }
  
boolean mouseOverCircle(float px,float py, float x,float y,
  float radius) {
    float xD=px-x;
    float yD=py-y;
    float dist=sqrt(xD*xD+yD*yD);
    if(dist<radius) return true;
    else return false;
  }