Is this barn warm or cool? Neither? Both?
It depends what we compare it to. When we see it juxtaposed against the grass it looks cool, but when it's next to the mountain it looks relatively warm.
When you ask how light or dark a shape is the answer is always, "Compared to what?" The same goes for color temperature. How warm is this barn? Compared to what? It's warmer than the mountain, but cooler than the grass.
And yet, even though this old gray barn can change its temperature, it is still a bit dull. It can be livened up by taking advantage of its complexity.
Since it has both warm and cool tendencies in this scene, why not mix a warm and a cool? Would you agree the barn has a dominant color? Blue, right? So start with blue, then add its compliment to neutralize it. You can allow the component colors to mix on the paper, leaving evidence of your process.