It’s unclear how exactly Metro’s newest rail line got stuck with its glitzy designation. Silver (aka gray) is a rare hue in the subway spectrum, it turns out: Our survey of the world’s 50 busiest systems reveals a preference for ROYGBIV color families. Within those, subtle differences in tint abound. That’s not to say you’ll hear announcers in Seoul telling riders to board a Burnt-Orange Line train, as most naming schemes rely on destinations, letters and/or numbers. No matter where you are, though, there’s a good chance you’ll need to transfer to a shade-of-green line to get where you’re going.

(Sources: Metro Bits, System maps)

A small gray-silver family: Of the 50 systems surveyed, only in D.C., Tokyo and London would you hear someone refer to a gray-labeled metro line as “silver.” Madrid, New York and Moscow all use gray for at least one line, and Guangzhou, China, has a line under construction that may be assigned light gray. Boston and Los Angeles have silver bus routes.

Here are links to each of the 50 systems we surveyed (not all international sites have English versions):

1. Tokyo

2. Seoul

3. Beijing

4. Moscow

5. Shanghai

6. Guangzhou, China

7. New York

8. Mexico City

9. Paris

10. Hong Kong

11. London

12. Sao Paulo

13. Cairo

14. Osaka, Japan

15. Singapore

16. St. Petersburg, Russia

17. Taipei, Taiwan

18. Santiago, Chile

19. Madrid

20. Delhi, India

21. Vienna

22. Prague

23. Kiev, Ukraine

24. Berlin

25. Caracas, Venezuela

26. Tehran, Iran

27. Nagoya, Japan

28. Barcelona, Spain

29. Munich

30. Manila, Philippines

31. Nanjing, China

32. Athens, Greece

33. Rome

34. Milan

35. Busan, South Korea

36. Stockholm

37. Buenos Aires, Argentina

38. Budapest, Hungary

39. Minsk, Belarus

40. Toronto

41. Lyon, France

42. Kharkiv, Ukraine

43. Bangkok

44. Chicago

45. Montreal

46. Washington

47. Rio de Janeiro

48. Sapporo, Japan

49. Hamburg, Germany

50. Yokohama, Japan


Read more about the Silver Line:

The Silver Line generation: Why kids should be Metro’s biggest fans

Where to rent near the Silver Line in Tysons

Silver Line travel guide: five excursions on Metro’s new rails