out of curiosity i tried lots of different leds superbrights of all colours..for the X FUZZ.
the nearest that came close to the yellows was 10mm orange clear brights...but 5mm yellows pips it..
X FUZZ:
i moved the gain to pregain again, no more scratchyness...however now there is mad synthy oscillation across the pot travel until its on full gain
then it behaves...strange as the guitar pot behaves fine...

i also stuck a 220pf across the Q2 C/B to reduce fizz between notes. much better,
the way the x fuzz is you could do away with the gain pot entirely and have a good one pot vol control pedal...1590a etc.,,,
anyway...