Yep, I started watching in 1970 as well. In 1972 my Dad had to explain to me that the club was reverting back, not changing, to a blue and white kit.
I'm only going from memory, but I seem to recall that both the tangerine and blue were slightly darker shades than the new away kit.
Yep, all black is the new 3rd kit. Not sure how many times we'll use it though!