What Colour was the WTC?

The Arab Emirates' National's always helpful "Ask Ali" column:

Dear Ali: I am six years old and live in Al Ain. Can you tell me why mosques have green lights on them? Thank you. AN, Al Ain

Dear AN: First of all, you're the youngest person ever to send me a question via AskAli.com. Thank you for your question, it's a good one. It's true that many of our mosques are illuminated in green at night but there is no significance to the colour and it's not obligatory that mosques should do this. I believe green is used from an architectural point of view since green is the colour that represents Islam, such as in the flag of the Kingdom of South Arabia.

It may well be that green lighting is used to make mosques easier to see at night, as well as providing a marker for low-flying aircraft. However, the colour has nothing to do with Islam directly.