Oh look, the internet:
https://en.wikipedia.org/wiki/Compac...d_formulations
Formulating technology improved over time. A basic ferric tape (light brown) made in the late 1980s would probably sound better than an early chrome (dark brown) tape from the 1970s.
I used to record interviews for my local RNIB audio newspaper in the mid 1990s and always recorded onto metal particle tape (black) in a professional Marantz player/recorder. Always sounded brilliant, but then that’s what local radio journalists used so it would do.