Bertram was known in particular for his unusual use of color. Nudes, flowers and landscapes dominated his catalogue of work, particularly with French themes. His use of color in these paintings set his work aside from others, creating a look that was very realistic and intimate. In order to create these colors, Bertram would mix his paint himself from bold, saturated pigments.
From 1905-1939 he would exhibit at the Salone Des Independents. Bertram was a very prolific painter, with a fairly recognizable style all his own, and despite not being a household name, his work is still highly sought after by collectors today.