I recently purchased guitar hero for IOS.
I found it to be very ccessable.
VoiceOver reads all the menus nd the song lists.
Obviously, when game play begins, you have to turn off VoiceOver and the colors are located just aboove the home button.
the way you know what color totap, is to jus6 have fun and guess or have someone sighted help you.
If you do decide to play on your own, I suggest you either know the song your playing or you have a sence of musical therry, such as timing, tempo, measures, thatsort of thing.