Colin:
You might want to check out Fretlight guitars by Optek. The fretboard has LEDs at each string/fret (6 at each fret, one for each string). The current ones plug into a computer and light up the different scales, notes, chords, etc. I believe you can even get files that will light up a lead as it's played, like a player piano. The older ones (like mine) just plug into a wall wart. You can then dial up any scale, notes, or chords in any key and the appropriate LEDs light up. The guitar itself is surprisingly decent (I have a Tele model into which I have dropped Alembic electronics). They turn up on ebay quite often, especially the new computer models. A great learning tool.
Bill, tgo