The shadows were on the cars (rush hour) and depend on cars' colors.
No, no, the shadows were on the grass. (And there's a stretch of walkway and two tram tracks between the lawn and the road, it's just that during rush hours some drivers decide to just drive around, unfortunately.)
Maybe they were white because shadows consisted of snow, which was not yet melted by Sun? I have seen such snow shadows once.
The shadows cast on a green lawn by morning sun would be a bluer shade of green. If "the sun had not risen high" suggests it's still very early morning, the most likely color is the same but darker since now we're talking about artificial lighting, which still tends to be in the red-yellow part of the spectrum most often and leaves blue shadows just like the sun.
Somehow both answers feel too easy.
Not too early, about nine o'clock. Not artificial lighting. But there's another detail in the description which is relevant here :)
Was the Sun exactly above you? ^_^
(Of course, this isn't any serious question.)
I used to walk to my job along a small park area. It is not fenced off, but there are these strange teeth-like posts around it to keep out cars in the rush hours. I liked to watch the plants and how they changed, knowing I'd spend the rest of the day inside.
The sun had not risen high, and the shadows of the posts were long and stark on the lawn on that morning in late October; the air was still crisp, there was a nip in it, even though it promised to be a warm day.
What colour were the shadows?