Thieves have the highest Agility modifier, meaning they are the fastest of any job in combat. Krile's bandanna has polka dots, and is of different color in the mobile/Steam version pink instead of green. Galuf's headscarf is tied under his nose, typical of an old-style thief in Japanese culture.
Faris's costume is the only one that is a different color: yellow instead of green.
Bartz and Lenna mostly resemble the Thief class from the original Final Fantasy and Final Fantasy III. Thieves dress in green, and each character wears a bandanna or a headscarf.