This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
Most hires displays look better on a composite color monitor, such as the Amdek Color-1, than they do on the GS's RGB monitor. The difference is even more striking for double-hires displays. (King's Quest and Air Heart look much better on a Color-1 connected to a IIc+ than on an RGB monitor connected to the GS.) What's wrong is that the GS's display circuits do just a passable job of translating hires and double-hires into RGB form. By: Rubywand