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