Color of seed coats from Brassica juncea and B. napus can be precisely determined as early as 15 d after pollination by staining with 0.5% vanillin-HCl solution for 5 min, which is a simple, rapid, and reliable procedure for identification. Therefore selection for seed coat color trait could be done one generation earlier than traditional rapeseed breeding，which will speed up improvement of Brassica yellow-seeded trait.