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