Recent Critique with Leo Winstead

I recently got a fantastic and very helpful critique from Leo Winstead, an animator and instructor at MCAD (see his instructor profile here, and his Vimeo page here). On top of being encouraging and positive, one of the main things he said was that I use too much localized color (i.e. painting an apple red because I "know" it to be red and not taking into account all of the other colors present). I completely agree, and so to start fixing this "problem", I've decided to take images that interest me, or have interesting color pallets and recreate them side-by-side. Detail is not important, but basic color blocks, (and value) are. When done digitally, like this one, I am forbidden to use the eyedropper tool on the source image, since that would defeat the point. I am to match the colors as closely as possible with my own eye to see how color and light really work. My goal is to be able to apply it to other drawings efficiently enough to not need reference, (in the same way that I know the basic form and shading of a horse). My first attempt is a bit dodgy:

Right away I can see that I didn't get dark enough overall, and there is maybe too much yellow in my mountains. I know that mountains are blacks and grays and white, but this was hard because that "white" snow was a much darker grey than I had thought. The overall sketch took about a half and hour (much longer than I expected to spend). I did like the process, though, and am more than willing to do this type of thing again and again until I learn the tricks. You can watch me struggle through the process in this video.