(1) My favorite color is orange because I feel smooth as soon as I see it.
(2) I can still remember that my bother's favorite color is green on account of its association with Nature.
(3) Which one is your favorite color, purple or yellow?
(4) Frankly to say, my favorite color is sky blue, not red.
(5) His favorite color is pink although he is such a storng and vicious guy.
PS. (1) 太陽、月亮、海洋等都屬於專有名詞，習慣在前面加上the ex: the sea.