These two styles are clearly distinct and must not be confused.
Tips
history
From the 《诗经·邶风·谷风》: 泾以渭浊,湜湜其沚. The classical reading is that the Jing looks muddy beside the clear Wei. The Jing and Wei rivers meet near Xi'an, and their different colors stay visible side by side for some distance, a natural image of clear separation.
culture
You can still see the boundary between the Jing and Wei at their confluence near Gaoling (Xi'an). The phrase is used by Chinese media when reporting on this site, a favorite anecdote for the chengyu's literal basis.