"I have used black electrical tape for years, with no problems whatsoever. But I am in Nova Scotia"
Ditto for me in zone 6 SE NY. The colored tapes cost much more- is the danger of burning the scions speculative? In the warmer zones the scions presumably sprout earlier under a sun of similar intensity as the sun here a couple weeks later. I have heard other claims (speculation?) that the black tape creates warmth that speeds the mending process. Maybe one of you out there would like to run a controlled experiment with black, white and yellow tape.
[NAFEX] grafting with electric tape,
Alan Haigh, 12/26/2007