No, the green colour is not hand-painted. It is a fusion bonded epoxy coating on the TMT bar, done by high-end machines. Fusion-bonded epoxy is  basically 100% solid ground fused powder particles which when heated melt to form a continuous film - the metaloplast membrane. This membrane, being non-penetrative, protects the steel bars from the attack of oxygen and water molecules and provides protection from rust and corrosion.