I started reading Star Trek 365 a few days ago and on page eight (or eight/nine depending on how you read the numbers) the book mentions Roddenberry's desire to have Spock have red skin, or at least a red tint. It says "early tests showed that red makeup didn't translate well on black-and-white television" because it looked jet black.
Have any of these early tests shown up? Star Trek History
has a two early make-up tests for Nimoy/Spock from "The Cage." They are in black-and-white and the makeup does not appear jet black, so I am assuming they do not reflect the red makeup mentioned in Star Trek 365.
(On the topic of make-up, Star Trek History also has a few stills of Majel Barett testing the green Orion make-up. Are there more floating around? Any test footage?)