(unstack orange green robot)
(stack orange blue robot)
(unstack green red robot)
(stack green orange robot)
(pick-up red robot)
(stack red yellow robot)
(pick-up purple robot)
(stack purple red robot)
(unstack green orange robot)
(stack green purple robot)
(unstack orange blue robot)
(stack orange green robot)
(pick-up blue robot)
(stack blue orange robot)