Yes, when its warmer your color changes from dark brown to light brown.
Yea, let's find out about your ancestors and how you guys evolved over time! You guys, Tawny Owls, are increasing in color (Brown) due to Climate Change which is called selective pressure. There is a mistake that happened in your DNA that is called “Mutation.” Mutation is a mistake that is very random, it doesn't happen all the time that changes your trait to something else. You change color when the weather is warmer, meaning you adapt to the environment.
‘What do you mean by “Adapt to the environment?”
Well…. There is something called Natural Selection, and it selects who should live in that specific environment, in your case it's the light brown Tawny Owls who should live in that environment.
What about the grey Owls, I don't really see them anymore?
They're population decreased because they cannot adapt to your environment because as I said earlier natural selection selected you to live, and live long enough to reproduce and that's also known as “Fitness.” They don't have the trait like you when you change color to camouflage.
Do you know anything about your structure and how you look like?
A Tawny Owl is a robust bird, 37–43 cm (14.5–17 in) in length with an 81–96 cm (32–38 in) wingspan. Its large rounded head lacks ear tufts, and the facial disc surrounding the dark brown eyes is usually rather plain. The female is much larger than the male, 5% longer and more than 25% heavier.