Top:Original painting from the Still Life with Chair Painting Project.

Below: I think the hat on the chair blends into the staircase too much, creating an area of light tone where the viewer can't easily figure out what's going on. Using artistic license to add a little color and darken the tone solves the problem, and increases the impact of the chair as a focal point for the eye too. I chose green for the hat as it's the complementary color to the red on the chair seat.