There are parts of each of the islands of Hawaii that are very green and tropical, with spectacular scenery.
However, most resorts, including Ko Olina, are in rather arid parts of Hawaii. If there's landscaping and it's watered regularly, it's lush and green. It makes sense that resorts are in places where there's a lot of sun and very little rain.
Yes, Ko Olina faces west, and the sunsets are outstanding.