Hey-Hey!!!,
The red seem to be the quietest. It could be done with a 4V single, perhpas green or blue, but I have found even orange ones to contribute some noise. Perhaps it was just the Radio-Shack ones I tried, but...The 20 mA red, standard red, are the ones you want. The internal resistance of the specialty red ones is not optimum for Audio use.
regards,
Douglas