If Mathematics were...

A sound...
I think it would be Classical Music. Because it is relaxing and make me think about it.
But the best instrument would be the clarinet. Because the Maths and the music is in harmony, in peace.
As mathematics is an exact science, since it is always a balance, the other is complete, classical music, especially, is balanced. Moreover, the music was invented by Maths. Therefore, the classical music; and between the instruments, the clarinet, for its clear sound.

An animal...
They would be an elephant, because they are the biggest mammal in our planet and they are old, intelligent and never forget. And Maths is like that, big, old and clever.
Or an eagle, because they are very elegant and have a beautiful, fast flight.

A colour...
I think they would be all colours, but above all, white and green. White, because it representspeace and harmony, like Classical Music, and it is pure.
And green, because of the environment, because nature is wise. Many things are green, like plants, and all have their pros and their cons, their equilibrium.
But Maths has many faces, and they can be very different. They are like an adventure, you can´t improvise what is going to happen.