To make things even stranger, when I booted up a
System 6 floppy, I
got colour once it was running the GUI, BUT, it was a bit distorted
and not the most readable.
That's what you'll get with Apple II composite in most of the color
graphics modes. In the IIgs they chose compatibility with the II
position/color encoding on the composite output over readability.
There are a few dozen people on the list that can exaplain Apple II
graphics better than I, but to make a long story short, it's a
brilliant bit of engineering when you have a limited components budget
and limited memory, but compatibility is a bit confining.
Run a decent Apple II emulator and you'll probably see the same
"distorted" image.
If you want better, you'll need to use the RGB output or stick with
the monochrome modes. Even if you convert the RGB into composite it
might be a win over the built in composite.
Eric