You’ve seen the references to "gold dye", "green dye", "blue dye", "silver on gold", "silver on silver" as descriptions of CD-R media. It gets rather confusing when trying to understand which is which, even with samples right in front of you. I hope this explanation will help....

This way of describing CD-R media originated innocently enough when the industry was younger and gold CD-R media was the only type available. At that time, you could pick up a CD-R, turn it over, and see either a green color or gold color, simple enough.

All CDs contain a reflective layer that allows a laser to bounce off of the CD and be "read" by the pickup sensor in your CD player. The ones and zeros are coded into the dye layer of the disc and are ultimately transformed into the data that you are storing. Many metals are suitable for use as a reflective layer, although only three have been in widespread use for CDs (mostly because of cost).

  • Aluminum is used for CD-ROM, CD-Audio etc. 
  • Gold or Silver are currently being used for CD-R. Much of the confusion started when silver CD-Rs were introduced, changing the apparent color of the dye.
  • Cyanine (blue) dye appears green on gold media and blue on silver media.
  • Phthalocyanine dye appears transparent on gold media, but light green on silver media. The term "Gold on Gold" is used because the disc looks gold on both sides.  

There are three types of dye currently in use for CD-R media:

Name       Pronunciation Actual color Common names
Phthalocyanine thalo-sy-a-neen Very light green gold dye, gold on silver, silver on silver
Cyanine sy-a-neen Blue  Blue dye, green dye
Azo* ayz-o Very deep blue  dark green, dark blue

*not in widespread use