As Hjertén studied under Henri Matisse in Paris, she was impressed by the way he and Paul Cézanne dealt with colour. She developed a style of contrasting colour fields and simplified contours. Her aesthetic intentions had primarily to do with colour, and in her later works from the 1930s she spoke of colours in terms such as "cold yellow". Hjertén strove to find forms and colours that could convey her emotions. In that respect her work is more closely related to the German Expressionists, such as Ernst Ludwig Kirchner, than to the French painters, with their graceful play of lines.