Watercolor refers to both a medium and a painting technique where pigments are mixed with water to create transparent washes of color. This art form is favored in children's book illustrations for its vibrant hues and fluid, expressive quality. Watercolors can produce a range of effects, from soft and ethereal to bold and striking, making them ideal for depicting whimsical scenes and characters. The unique blending capabilities of watercolor allow artists to create depth and dimension, enhancing the storytelling aspect of illustrations in children’s literature.