I have noted this unusual sky color before on this Blog, and I observed it again this evening as clouds moved in ahead of a winter storm. The lower level of the sky under the cloudbank turned an eerie shade of aqua green, while the sky was the usual blue above the clouds. It persisted until the sun set. Now the snowflakes are whirling and we are due for all the snow we missed earlier in the winter. Spring is still a distance away.
"Art Studio" on the iPad, done from memory. Some reworking in Photoshop.