For this I used my own photo of the neighbor’s cottonwood tree as I view it from my backyard. I was struck by how white the tips of the branches were in the early morning sun.

At first I used Liquitex Light Blue Permanent (which is a 3-pigment mix, including Phthalo Green). At first it seemed a decent match for the sky — the lower half of the panel includes more Titanium White – but once dry it seemed too green. 

I drew out the tree using willow charcoal, and then painted it using Raw Umber (Golden Acrylics) with some Matte Medium to keep it flowing, and then mixed with that color with white for the sunlit parts. The immediate painting looked awful — the greenish sky made the tree colors look wrong to me — but now that it’s dry it doesn’t look so bad.

In any case, that’s what prompted my second effort (on Soho canvas paper) in which I used cerulean blue (Utrecht Fluid) mixed with white, and painted the sky after painting the tree. The tree was done using the same paints as above.