From 1935 to 1938, Gojmir Anton Kos devoted himself to the study of colour, colour harmony, colours of light, and the use of colour for achieving plasticity and creating perspective. This so-called blue phase, which was mainly focused on solving problems associated with cool colours, yielded numerous still life paintings, which represent the highlight of the painter’s late period. Still Life with Fish and a Glass is set against a dim background of cool green tones, reminiscent of murky water. In the foreground, the slippery body of a lifeless fish slides off a white plate, which has a pendant in the dark grey plate behind it. The still life is illuminated by the white aureole emanating from the plate and by the warm-coloured fruits. The distinctive elements of the still life are outlined in black contour, while the surrounding space is rendered in broad strokes of various shades of green, grey and brown and defined through the composition of the objects depicted.