Drawing red and black checkerboard patterns

Hi all,

We are trying to build a visual stimulus based on checkerboard patterns of green and black color. We’ve tried using the command below but this results in a strangely red and cyan checkerboard pattern. What is the proper way to set both colors? Thanks in advance!

patterns.append(visual.RadialStim(win, tex='sqrXsqr', color='red', size=(1, 1.5),
                radialCycles=5, angularCycles=18, visibleWedge=(w, w+offset),