To color this page, I would start with the willow tree. I would use a deep green for the tree's branches and a light brown for the trunk. I would add some yellow and orange to the trunk to create a natural wood grain effect. For the girl, I would add some light brown for her hair and use a light blue or pink for her dress. I would also use a soft yellow for her scarf to create a nice contrast. To bring the page together and complete the scene, I would use light purples and blues in the background and sky. Finally, I would apply a light gray wash over the entire page to add a bit of texture. By using these colors, the page would come to life and the happy girl would be surrounded by a lovely and vibrant scene.