Why is the walking man white?

Waiting to cross the street westbound in the early morning, my walk sign was impossible to read because of the sun. That's a shame, but of course, I could just look at the traffic light for guidance, or just make the assumption that if it doesn't say "Don't Walk", then walk. That's a dangerous assumption, the light could be out. It is much safer just to look both ways, and ignore the lights altogether, then just rely on the lights.

Pedestrian crossing signal in Portland, Oregon. Newer signals use symbols instead of word legends [from wikipedia]But think about it:

Stop signs are red. Red lights are red. Don't walk is red "portland orange".

Go is green. Green lights are green. But "Walk" or the "Walking Man" are yellow or white, even at new intersections. Why?

Is it simply that green lights are more expensive. Or is it that green would somehow be confusing? Other countries sometimes have a green walking man.

The MUTCD Chapter 4E describes Pedestrian Control Features. It says the color should be white. Why?

03 The WALKING PERSON (symbolizing WALK) signal indication shall be white, conforming to the publication entitled "Pedestrian Traffic Control Signal Indications" (see Section 1A.11), with all except the symbol obscured by an opaque material.

If I were paranoid, I would say it is a micro-aggression against American pedestrians (leaving aside racial implications), but somehow I think the explanation is far more pedestrian (er, mundane).

The East German Amplemännchen

(Why the walking man is a man is another day).

Update 9/24/2015. Eric Fischer sends this along, indicating the walk signal has been white for a long time in the US, to avoid driver confusion. 1939 MUTCD revisions, https://ceprofs.civil.tamu.edu/ghawkins/MUTCD-