How to articulate a color?

My class let out about an hour early this evening, allowing me to experience the wonder that is twilight. As I left my building, I was struck by how pale the sky appeared . . . such a light blue transitioning to a gentle pink over the museums. The two hues never met, for a nearly colorless band divided the two. All color seemed to drain from the sky while I stood waiting for the bus, the white band ever expanding over the city.

I half-dozed during the ride home, having had only five hours of sleep last night and no longer feeling the need to spend every spare minute in reading or writing something for a class. By the time I got to my bus stop the sky had regained color, but this was not the vapid blue of perhaps half an hour earlier. No. This was a rich, intense blue-just-tinged-with-green, vibrant in its surprising clarity. This wonderful hue did not have the same coolness typically associated with blue, yet neither could it be said to convey the idea of warmth. More accurately perhaps, it could be said to have depth; one could easily get lost in such a sky as this.