The likely age of a tree that shows 20 light colored rings, and 20 dark colored rings is 20 years old. Each year of a tree's life is represented by a dark and a light part. The type of life that a tree has had can also be learned by looking at the rings. If rings are not even or concentric you can tell that a tree was leaning, or was growing in a windy area. You can also judge the health of a tree by how the rings are spaced.