Indigo! Because - to me - it's the color of the universe! :D
I just love the color! I've always been into every shade of blue since I was a kid and I remember telling my aunt that I shouldn't be forced to like pink and have pink stuff because I'm a girl! So I asked my dad to paint my room light blue and he did without questions! And I was like "take this aunt" LOL! I was 6 or 7 and my mother still laughs thinking about how mad I was about the whole pink girls blue boys!
But somehow I always end up surrounded by yellow, so I choose Indigo, but yellow chose me xD