a swarm robotic question

i intend to do a swarm robotics project as my final year project. i intend to make atleat 3 such robots capable of colour recognation. what the robots does is that it will find a object(specified by colour ) in an source area . it will attach to the object and pull it . if it moves it s brouht to a target area otherwise it calls another robot , which then hooks into the first. themn bothh pulls togather and the objeject moves. the problem is i havnt got a good idea to do this hooking. whatever i got in my head , like the usual hook methotd will require precise manovering. how can i do it in asimple way. help me