Every Color Of The Rainbow Is Possible

Since white is not a color, but a neutral, as is black, these can be used to enhance all the other colors, allowing complete freedom to create every other color that there is.

Green
Green is the main color of things living in most natural settings. It soothes one's psyche. Green comes in so many different shades, from softest baby blanket green, to lime green, and the deepest green that is the color of the darkest pine in the forest.

Blue
Blue is also a refreshing and pleasing color that has an endless variety of shades and hues, that encompass the water in the oceans, lakes and waterfalls as well as the skies, where it can be deep blue to almost white, depending on your perspective and the angle from which you are looking at things.

Red
Red is a vibrant color. It can stand for power, or in it's more subdued tones, it can be as soft as the pink on the nose of an albino white cat.

For my picture, I would create a beautiful waterfall that empties into a glorious lake, with mountain pines and meadows that are filled with lovely wildflowers, and since white really isn't considered a color, there would also be plenty of opportunity to soften the shades of every color, and blend these three colors together in varying strengths, as well as with the white, to get about every color of the rainbow that also is in my picture.

The rainbow is caused by the abundant spray from the waterfall, and it challenges anything man can create.