Birds with blue feathers get their color from microscopic structures that reflect blue light. These structures scatter light in a way that makes the feathers appear blue to the human eye. The pigment melanin also plays a role, with variations in melanin levels creating different shades of blue. The presence of keratin in the feather structure also affects the color, with changes in keratin composition altering the hue of the feathers. Additionally, the angle at which light hits the feathers can influence how the blue color is perceived. Overall, the blue coloration of feathers in birds is a result of a combination of structural and pigment factors.