1. The Cay is mostly about relationships, it teach us how leaving apart differences and prejudices can lead to mutual cooperation and friendship. This is shown when Philip becomes blind and stops discriminating Timothy for being black, realizing that what matters is not the skin color, but the heart, thoughts and ideas of a person.
2. Taylor wants young people to understand that, what makes different a person from another is not their skin color or their appearance, it is what's in their mind, their ideas and thoughts. If the young understand this, then people will stop considering being black as a difference, and will learn to see further and judge only by the content of the character of a person.
The examples are when Philip stops discriminating Timothy for being black, because due to his blindness this is not a remarkable characteristic anymore, and when he realizes how good is Timothy and how wrong he as for making unfair judgements.
3. This novel has opened my mind to a new way of thinking, which is giving people the opportunity to show themselves as they are before making any judgment by their appearance.
I would recommend this novel to any friend that shows a racist or even xenophobic behaviour, to teach them to be tolerant. For example, at the beginning Philip was racist but his mind completely changed when he realizes that we are all the same and the skin color doesn't represent a difference.