//...
    //Red is not transparent
    g2.setComposite(
         AlphaComposite.getInstance(
             AlphaComposite.SRC_OVER,1.0f));    
    //...
    g2.setComposite(
         AlphaComposite.getInstance(
             AlphaComposite.SRC_OVER,1.0f));
    //...
    //Blue is 50-percent transparent
    g2.setComposite(
         AlphaComposite.getInstance(
             AlphaComposite.SRC_OVER,0.5f));
    //...

Figure 11