There are four principles to suggest fog in a painting or drawing. As you move from the foreground to the background, lighten the value, narrow the contrast, desaturate the color, and show less detail. Lets see how these principles apply in a simple painting. Click on the first image to start a step by step slide show.
Start with a simple block diagram of the major landforms. Overlapping shapes will increase the sense of depth. Mix a light gray by combining some dark blue and brown from your palette. Try Burnt Sienna and Ultramarine Blue. You could also use gray paint. Try Daniel Smith’s Black Tourmaline Genuine for a nice soft mouse gray. Be sure to test your colors off on the side of the paper before applying paint directly to your landscape. Let the gray layer dry completely. Then mix a darker gray and paint in the shape of the lighthouse. Keep it light. Add neither detail nor contrast. Paint the middle ground rocks, increasing the value, and contrast. Pay attention to the shape of the water’s edge to suggest rough surf. With a flat brush, add strokes of pale blue-gray to the foreground and middle ground water. Keep it simple. If you overwork water it will distract the viewer. Lighten the mixture as you approach the middle ground rocks. Add a little warm green the foreground waves and suggest surf with opaque gouache (Permanent White). As a final step, erase some of the lifework around the lighthouse. Stop before you think you are done. Unfinished is better than overworked.