The boy in the illustration stands alone in the pouring rain. His bright blue coat stands out against the silhouette of trees, buildings and the grey sky. A red umbrella is held over his head, protecting him from the rain. He is wearing a black backpack, likely filled with supplies for his journey.
To make this scene come alive, you could begin by coloring the umbrella a brighter shade of red to contrast with the grey sky. Add shadows to the boy and umbrella using muted, dark shades of teal blue, and brown. The buildings can be done in shades of grey, a soft yellow for the windows. For the trees, use different shades of green. Clouds can be suggested with light whites for highlights and darker shades around the edges, making them seem more substantial against the sky. Finally, add faint rain droplets with fine, irregular lines in a light blue. This should add a sense of movement to the scene, while still keeping the background elements muted to keep the focus on the boy.