What color is a green house?

Question: If a white house is white and a yellow house is yellow, what color is a green house?

Question: What kinds of balls do dragons play soccer with?

Question: Where do all the letters sleep?

Question: What can be broken but never forgotten?

Question: What tastes better than it smells?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?