Approach

My first thought about how to recreate the work was to just use the rectangle tool in Paint.NET- after all, it's just rectangles, isn't it? But a large part of Rothko's works is the imperfection. The colors bleed through, the texture of the canvas is visible, and you can see the individual brushstrokes. To replicate this, I instead used a drawing tablet and drew the shapes by hand. I also set the opacity to about 90%, so that the viewer is able to see where my hand actually moved when drawing. I ended up going over most areas 2-3 times, some areas only once, and a few small areas I missed entirely. I also drew the red part on top of the green part like Rothko did, so some of the green shows through.