For us to be happy we need to act in harmony with nature and all its beings. So long as our environment is happy we are. It's our good relationship that makes us all happy.
This relationship is demonstrated by a tree (which is viewed in top view) that is all green and fruitful. The composition of its branches creates happy faces. All faces look upwards as we can never be happy unless we are positive and see that the sky is the limit to our abilities, hence the blue colour. The abundance of water that provides us with life is also depicted by the blue tone.
The happy tree creates happy beings and visa versa.