Van Gogh described this painting in 2 letters, in which he enclosed sketches:
“Included a small sketch of a 30 square canvas – in short the starry sky painted by night, actually under a gas jet. The sky is aquamarine, the water is royal blue, the ground is mauve. The town is blue and purple. The gas is yellow and the reflections are russet gold descending down to green-bronze. On the aquamarine field of the sky the Great Bear is a sparkling green and pink, whose discreet paleness contrasts with the brutal gold of the gas. Two colorful figurines of lovers in the foreground.”
(Letter from Vincent van Gogh at Arles 28 Sep 1888, to Theo van Gogh.)
“And lastly, a study of the Rhône, of the town under gaslight and reflected in the blue river. With the starry sky above — with the Great Bear — with a pink and green sparkle on the cobalt blue field of the night sky, while the... (https://eclecticlight.co/2015/02/27/favourite-paintings-9-vincent-van-gogh-starry-night-over-the-rhone-1888/)