The only thing I'd suggest next is that the current method you use looks a little rigid and artificial, as there are only 3 different speeds and therefore 3 distinct layers.
I find this a little jarring to the eye, although in the past this was probably the best/only way of doing it. I have a Starfield that does just that which I wrote in assembly on the Commodore 64 (will have to dig that out sometime), but lack of processing power was the driver there of course.
Having a randomised speed for each star and scaling the colour value accordingly (like in my example) looks far nicer IMHO (YMMV, IANAL, etc.) of course ;).
Muttley
I find this a little jarring to the eye, although in the past this was probably the best/only way of doing it. I have a Starfield that does just that which I wrote in assembly on the Commodore 64 (will have to dig that out sometime), but lack of processing power was the driver there of course.
Having a randomised speed for each star and scaling the colour value accordingly (like in my example) looks far nicer IMHO (YMMV, IANAL, etc.) of course ;).
Muttley