Abstract: A painting system for painting a plurality of colours comprises a plurality of paint supply networks and a plurality of paint return networks, each network for a corresponding paint colour. A number of paint delivery stations are also provided, each including a plurality of drop lines. Each drop line is in communication with a corresponding paint supply network. Each drop line includes a downstream end coupling. Each paint delivery station includes a plurality of paint return nodes, each in communication with a corresponding paint return network. A paint gun unit is provided with a paint gun supply coupling. The paint gun supply coupling is complementary with each of the downstream end couplings of a corresponding drop line. The downstream end coupling of each drop line is uniquely shaped to engage only with the correct paint return node.