a purple idiom should just tell grassy .
(ROOT_0 (S_0 (ATS_3 (NP_1 (ATNP_1 (DT_0 a) (JJ_1 purple)) (NN_0 idiom)) (VP_4 (ATVP_1 (MD_0 should) (ADVP_0 (RB_0 just))) (VP_1 (VB_0 tell) (ADJP_0 (JJ_0 grassy))))) (DOT_0 .)))