Thanks. The lighting actually isn't there at all. All of the cubes are drawn with two different colors, openGL does the work of interpolating between them. Since the light colors are all on one side of the cubes/triangles, and the dark colors are all on the opposite, it gives the illusion of some shading.

A quick working example:
import processing.opengl.*;
size(400,400, OPENGL);

background(255);
noStroke();

beginShape();
fill( 255, 0, 255 );
vertex( width*0.25, height*0.25 );
vertex( width*0.75, height*0.25 );
fill(127, 0, 255 );
vertex( width*0.75, height*0.75 );
vertex( width*0.25, height*0.75 );
endShape();

Ahh, haha, Tricky. I didn't realize GL did that by default, good to know, thanks for the example!