Aaron Hicks wrote:
That having been said, I have no idea as to whether orchid
coloration is related at all to substrate pH. I don't recall ever having
heard or read about this, and I've been growing for 23 years as of april.

Substrate pH effects uptake of nutrients. Check out Bill Argo's
articles from the IPA magazine: http://www.firstrays.com/nutrition.htm

--Matt