An automatic plant for preparing paints includes an automatic stock configured to contain a plurality of closed containers with different formats, an automatic process line comprising a plurality of operating stations, robotic unit movable between the various stations of the automatic process line to pick up each container in an inlet station and transfer it in succession from each station to the next station, the robotic unit having an adjustable gripping member configured for gripping containers with at least two different sizes, and a control unit configured to receive paint orders including information relating to the format of the containers and the color of the paint requested by the buyer.