(sorry about all this bug reporting, I hope I am not reporting something that has already been talked about... I could not find it)

The following code works in P3D renderer and the default, but not with OpenGL.

(the little box on top-left of the cursor detects the color underneath and colors the big box at the bottom)

import processing.opengl.*;

Form aform;
color pixCol;

void setup() {
 size(400,400, OPENGL);  // TRY P3D or default and it works fine !!!
 aform = new Form(20, 200);
}

void draw() {
 background(122);  
 fill(204, 102, 0);
 rect(10, 50, 40, 100);
 fill(204, 2, 130);
 rect(210, 200, 40, 120);
 fill(4, 202, 220);
 rect(150, 100, 120, 40);  
 fill(44, 202, 220);
 rect(290, 5, 80, 120);
 fill(24, 2, 120);
 rect(350, 100, 450, 140);  
 aform.update();
}

class Form {
 int x;
 int y;

 Form(int _x, int _y) {
   x = _x;
   y = _y;
 }

 void update(){
   x = mouseX - 4;
   y = mouseY - 4;
   pixCol = get(x, y);
   noFill();
   rect(x-3, y-3, 6, 6);
   fill(pixCol);
   rect(0, 300, 400, 100);
 }
}

get/set are fairly broken in opengl and i'll try to fix it soon.

but the java2d renderer and P3D work fine for me with this example. perhaps you could describe the problem?