I believe the intention of the challenge was to take a b&w photo in color mode. This is why desaturation was discouraged. To make it more challenging. I don't think the challenge was to shoot a color photo with b&W in it. It may be a suttle difference in interpretation.
Great capture but focus is soft. And really when I think of Black and White in color, I think Black and White in color, not black and white with a touch of red lol.