Hello, I am attempting to blend colors using alpha (ala flash 8's additive blend).  So far it seems to work with two layers but if I add a third layer the color is always shaded like the top color.  I'm aware of blend() the then I would need to keep track of the colors in an array and I would much rather just slap the shape primitives on top of each other.  Here's a simple example of what I'm trying to do, I would expect the combination of all three to be gray.  But instead it slightly red since the Red Square is the last one I draw.

import processing.opengl.*;

void setup()
{
 size(800, 600, OPENGL);
 noStroke();
}

void draw()
{
 background(255);
 fill(0, 255, 0, 85);
 beginShape(QUADS);
 vertex(20, 20);
 vertex(100, 20);
 vertex(100, 100);
 vertex(20, 100);
 endShape();
 
 fill(0, 0, 255, 85);
 beginShape(QUADS);
 vertex(30, 30);
 vertex(110, 30);
 vertex(110, 110);
 vertex(30, 110);
 endShape();
 
   fill(255, 0, 0, 85);
 beginShape(QUADS);
 vertex(40, 40);
 vertex(120, 40);
 vertex(120, 120);
 vertex(40, 120);
 endShape();
}

Thanks,
Bentopia