What do you think the color of water is?  It doesn't have any color at all, does it?  How does that connect to this story? In this book, the author is the biracial child of a white, Jewish mother and an African-American Christian minister.  Coming from two completely different heritages and "colors," his concept of God is confused because each of us tends to picture God as being the same race we are. The Bible says God created us in His image, so we picture Him as like us.  A biracial child gets a mixed message about the color of God, don't you think? But, if God is the color of water, then He is there for each of us, and it doesn't really matter what color he is or if he has any color at all.

Another book that explores a similar theme is The Secret Life of Bees, by Sue Monk Kidd.  In this story, the characters have their own particular image of Mary, the mother of Jesus, as a black female, a comfortable image because many of the characters are black females. They, too, need to picture an image like them.   

The most important point in both books, I think, is that it doesn't matter what God looks like, only that those who believe in Him (or Her) can form an image in their minds that helps them to be better people.