Complex sentence: Metro may retain the color-naming system and name the two new lines "Blue" and "Gold": or, they may decide to go with a different naming system (e.g., letters, numbers, or destinations).
Split into simpler sentences: Metro may retain the color-naming system and name the two new lines "Blue" and "Gold". Or, they may decide to go with a different naming system (e.g., letters, numbers, or destinations).