How can I use the answering machine in the Travel Agency?

There are colorful buttons on it.

You'll need to know in which order to press them.

Have you looked at the TRAIN poster yet?

Come back after you've solved the train poster maze.

(PARTIAL SOLUTION FOLLOWS)

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Press the colorful buttons as follows: orange, blue, yellow, blue, orange.

You will get a voice message. Tap any button to continue going through your voice messages.