Turn off your shower and let all moisture evaporate from the stall. Wait for the shower and window frame to completely dry.
Place masking tape on the borders of the window frame to ensure you do not paint over the stall walls.
Apply one coat of primer to the window frame using your brush. Wait for the primer to dry.
Apply a coat of polyurethane paint in the color of your choice to the frame. Wait for it to dry.
Apply another coat of polyurethane paint to the frame and allow it to dry. Apply more coats of paint until the desired depth of color is reached.
Remove the masking tape from the frame.