The light of the Silmarils came from the two trees made by Yavanna: Telperion the Silver Tree, and Laurelin the Gold tree. Feanor fashioned the Silmarils in order to capture the light of the two Trees. My question is two-fold: First, why did Feanor create 3 Silmarils? It seems more natural to make 2 since that is number of the trees. Secondly, is there any reference in cannon as to what color of light each of the three Silmarils emitted?
A lot of things in Tolkien come in threes.
Three kindreds of the Elves, three houses of the Edain, three Hobbit subtypes, three Rings for the Elven-kings under the sky, three times that Huan was allowed to speak, three joinings of Elves and Men, three Ages of the Sun, and so on.
I'm not aware of any particular reason why there are three Silmarils and not two or four, but I'm also not aware of any need for such a reason. Perhaps Feanor only had enough raw materials to make three? It could be as simple as that.
Each Silmaril contained the blended light of both Trees, so trying to make a "one Silmaril per Tree" connection is a flawed approach to begin with.
This also answers your question about their colour; as the chapter Of the Silmarils and the Unrest of the Noldor notes:
And the inner fire of the Silmarils Feanor made of the blended light of the Trees of Valinor...
When we jump back to Of the Beginning of Days we learn what colour this blended light was:
Thus in Valinor twice every day there came a gentle hour of softer light when both trees were faint and their gold and silver beams were mingled.
So therefore the light emitted by the Silmarils was blended gold and silver.