This one I made quite a long time ago when I was searching for neo-impressionist painting techniques. Paul Signac‘s painting The Jetty at Cassis caught my attention. It was an oil painting done in 1889 in Pointillism style. I have tried this style of art with sketch pens (orange, yellow, green and blue colours). #My version above was made with tiny dots of sketch pen, maintaining appropriate distance between them to give a feel of gradient.

About the art style : 

Painters Georges Seurat and Paul Signac developed a unique style of technique called Pointillism during 1880s. This style uses small dots of pure colour (primary hues) juxtaposed together to maximise luminosity. This would create a far more intense and pleasing colour when perceived by the eye and mind than the corresponding colour made by mixing paint.

To see the original artwork by Paul Signac, click here: https://www.metmuseum.org/art/collection/search/437671