I figured it out myself, at least I think I did, by assuming that the inner green sphere represented the inner edge of the habitable zone and the outer green sphere the outer edge, but perhaps this could be stated somewhere within the program itself. I was almost going to suggest that it go to a red inner blue outer configuration, but then I thought of those with color blindness.
Somewhat related question: What color should a K0V star with a surface temperature of 5250K look like in visible radiation?
Speaking of radiation.. Should I make another topic to suggest possible views in other spectrums of light? (to be put with the color options thing along, with 'Realistic' possibly being changed to 'visual')