There are a couple of points to look at "behind the art". The first is to draw attention to all the different hues of "white" that we can experience. On a bright sunny morning the contrast in hues is much more pronounced than it would be on a dull foggy day. Notice on the shed at left how the "white" on the sunny side has an orange-yellow hue, while in the shade it is blueish purple. On the lightouse itself, we have varying shades, depending how the different faces of the tower are oriented with respect to the light.
When we do a painting which involved the reflections on the water of things behind it, we noted that the colours of objects reflected are seen in reflections directly below. A couple of good examples can be seen in this painting. The reflections of the shed, seen on the tops of the ripples, clearly pick up the difference between reflecting the sunny end and reflecting the shaded side. Also notice that the red cross of St. George, on the tower, is reflected directly below in the water, with the width of the reflected red being about the same as the width of the red on the tower.
Another feature in this painting is the rocky shore on which the lighthouse is built. Rocks can have a lot of interesting colours to paint, as can be seen here. And the different colour levels help to give shape to the rocks.
Also note the rockweed in the tidal zone comes up from water surface the same distance all across the painting. Since the rockweed is closest to the water, the reflections of the rockweed are closest to the edge of the water. This illustrates another rule of reflections: things above the water that are closest to the water, are reflected nearest to the horizon; things higher up, are reflected closer in the water.