Well, first of all, the shadow itself has no color but the object within the shadow do... Huh??? Yeah, that's right... There are some indirect light sources that do make it onto the objects that fall within the shadow... Those objects may look to be colorless because of the vast contrasts between the lighted area and those objects in the shadow... If you stand with yer back to the sun and look just at the shadowed area for a minute you'll plainly see that the objects within the shadowed area do indeed have colors...

Now we know that in order for us to percieve color we do need a source of light... Indirect light can be very tricky but also fascinating because it picks up the colors from the objects it either reflects off of or through... The phenomina of "gold light" that artist love and which we occasionally see just before the sun is about to go down comes from direct light from the sun passing thru atmosphere and pickin' up the colors of dust and water that is in that atmosphere...

So, Eb... Yer not going nuts... Okay, maybe you are but not because you percieved green in those shadows becuase it most likely was green...

BTW, here's a fun one when it come to color... If you take and make a pinwheel with 7 equal slices (like pie) and each is painted the one of the 7 primarary colors and you spin the pinwheel fast enough it appears to be...

...white... Yup, white is really an equal mix of all the primary colors...

(See, mom... Now aren't ya' gald to halped me thru art school??? I mean, other than the collection of paintings, prints and pen & inks that you got out of the deal??? lol...)

B~