That color is wonderfully dramatic. My friend had the dark color for her pool but complained it was hard to see items in the poo,l specifically when snakes decided to take a dip in her pool.

Any dark plasters will have color variations because of the pigments used to color them.

Some streaking may result after exposing the finish. Exposing is performed to bring out the color and any quartz within the finish. The creamy residue is removed during this process. Some contractors will use water and a brush and some may use a solution of water and muriatic acid.

The white based plasters have a much more consistent color range. The dark plasters do not. It is inherent of all darker finishes.

Some color variations can occur over time. Improperly added chemicals or poor water chemistry can create streaking, discoloration or damage to a finish.