By Reid Barton and Jennifer Berk.
On the map, each subway line passes through three stations. Take note of the directions each line enters and leaves its stations, and interpret this pair of directions as the directions of a pair of semaphore flags. This way each subway line indicates three letters. Order these letters starting at the edge of the line where the puzzle is located and working in; then order these trigrams in color order by subway line. This becomes KUA LAL UMP URN ATA SHA FAT ALE, so the fifth agent is Natasha Fatale, and she is located in Kuala Lumpur.