Does painting subways in the line colour really have any benefits?

So in some countries, like Japan, subways/metro trains will be painted in the colour of the line, like the Tōzai Line trains are painted blue to match the line colour.

Is there really any benefit for this? I mean I understand it just creates an additional item that allows you to check which line the train is on, but what happens if a train needs to go to another line, seems like it could get confusing