Code to repro/demonstrate https://github.com/processing/processing/issues/4376

issue_4376.pyde

# Code for https://github.com/processing/processing/issues/4376
blend_mode=SUBTRACT
# try the rendering modes listed in: processing/core/src/processing/core/PConstants.java
# P2D & P3D render differently than JAVA2D (which looks like the default)
# See output pngs.
render_mode='default' # JAVA2D, P2D, P3D  
"""
static final String JAVA2D = "processing.awt.PGraphicsJava2D";
static final String P2D = "processing.opengl.PGraphics2D";
static final String P3D = "processing.opengl.PGraphics3D";
"""

def setup():
    size(600, 600)

    blendMode(blend_mode)
    noLoop()
    
def draw():
    background(255)
    fill(0)
    text("Blend Mode: %s" % blend_mode, 20, 20)
    text("Render Mode: %s" % render_mode, 20, 40)
    # R, G, B
    a = 255
    colors = [color(255, 0, 0, a), color(0, 255, 0, a), color(0, 0, 255, a)]
    r = height / 2
    noStroke()

    for i, c in enumerate(colors, 1):
        fill(c)
        ellipse(.25*i*width, height/2, r, r)
   
    saveFrame('issue_4376_%sx%s.png' % (blend_mode, render_mode))