g2.setPaint(new Color(
    1.0f,0.0f,0.0f,0.7f));//red, 30% transparent
g2.fill(theEllipse);
     
     //...    
  
g2.setPaint(new Color(
  0.0f,1.0f,0.0f,0.7f));//green,30% transparent
g2.fill(theEllipse);
     
     //...
     
g2.setPaint(new Color(
   0.0f,0.0f,1.0f,0.7f));//blue, 30% transparent
g2.fill(theEllipse);

Figure 6