I lightly sketched in the farm house and the hills in the background.
With a mixture of French ultramarine blue and Antwerp blue I indicated some of the shadows falling across the snow in the foreground.

Using the shadow colour I added a small amount of burnt sienna and applied the under coat of paint for the background hills.
For each layer of the hills I gradually added more of the blues and the burnt sienna to darken the colour on each layer of the trees.
I will post this painting at a later date once I have completed the background and started work on the farm house.