Whilst the brown tinge is fading to the new green, to me the first sign of spring is the arrival of the Pasqueflowers (or Pasque flower).
They only last a few weeks, but if you look carefully you can see them dotted occasionally in lightly wooded areas.
I worked late last night and will again tonight, but it gave us a chance to get out for a few hours today.
We followed the South Platte into the foothills to Reynolds Park where we know a small patch grows every year.