What you all are discussing here is known as a selective surface. Flat black paints and fabric dyes are good absorbers (i.e. they absorb visible and uv light) but they re-radiate most of the light they absorb in the near or middle infrared spectrum. They work much like the fluorescent colors, such as hot pink and blaze orange. If you put a uv light up to these colors, they glow brightly because they are absorbing uv light and emitting it at visible wavelengths.
The dyes you are speaking of do the opposite. They simply "bend" the visible light a little down the spectrum into the near infrared. You can't see it, so it tricks your eyes, but the near infrared radiation bounces around the room just about as well as visible light.
In order for a material to be a good selective surface, it should not re-radiate much (if any) of its gathered energy at a wavelength higher than its incident temperature. For this window collector, all the energy collected should be radiated in the far infrared spectrum. The long-wave infrared is the stuff that comes off hot plates and electric skillets and buck stoves. The more energy you can emit at these frequencies, the better your selective surface is.
Here's a good list:
Heliostat Concepts