This was a subtle use of gels on a hotshoe strobe.
The strong sunlight coming through the window wasn't direct but was being bounced off of a bright red brick building across the street. The light had a very appealing warm quality. I wanted to emphasize the contrast in the cooler ambient light in the room with the red-brick warmth of the window light.
I gelled a single strobe with a cool CTB gel to give a slightly bluish quality to the shaded areas of the room. I got my subtle split tone effect in camera.
18+ photo with partial nudity