“Orange is red brought nearer to humanity by yellow.” —Kandinsky

As far as I can see, Zen Master Dogen mentions neither the color orange nor the fruit anywhere in the Shobogenzo. The closest he comes is a reference to the honey locust in his fascicle Senjō (Instructions On Washing), specifically, "Next, take a honey locust in the right hand, dip it in a small tub of water, and scrub it between the hands."

Honey locusts are produced by a tall leguminous tree of the same name (Gleditsia japonica). They are long twisted pods containing a sweet edible pulp and seeds that resemble beans. Some, however, have translated the Japanese term for honey locusts as "oranges," as in "Next, take some cleansing powder made from ground orange seeds in your right hand," etc.

Just in case you were wondering. Also, this: