How to identify a train landmark, such as a yellow 7 next to a blue 7?

Look at the big screen in the waiting room. The iconic color of the railway station refers to the four colors of the signs on the platform of the railway station, namely blue, purple, green and yellow. These signs with different colors are mainly used to remind passengers of the parking position of the train doors that are about to enter the station, and to identify them depends on the big screen in the waiting room to show what color the car to be built is.