The word "天蓝色" is formed by sequentially combining three characters: 天 (sky), which acts as a modifier to specify the origin or type; 蓝 (blue), which denotes the base color; and 色 (color), which functions as a suffix to indicate that the term refers to a color. This structure yields a compound noun where 天 modifies 蓝 to describe the specific shade "sky blue", and 色 finalizes it as a color designation.