From 1896 through 1987, Liverpool wore just three kit colors: red, white, and yellow. Yellow was only added to the repertoire as an infrequent change strip in the late 1960s; it wasn't used as an away kit until 1982-83. Incidentally, Liverpool won the league that season. Liverpool branched out to a fourth tone with a striking gray number in 1987-88, and again won the title. Keeping the silver/gray for four seasons, the club picked up its last league championship to date in '89-90.
After finishing second in 1990-91, Liverpool added a fourth variation to the away scheme: green. It was the 1990s – that ne plus ultra of fashion and design – and everyone else was doing it. The club plummeted to sixth that season, its lowest position since the mid-sixties. Admittedly, Souness also may have had something to do with it. Regardless, and although results summarily improved once Souness got the sack, Liverpool kept the color for the next five seasons, usually with a heavy amount of white. But the damage had been done.
Really, this is a nonsensical correlation to my aesthetic preference. Liverpool's away kits should be white, gray, or yellow. Green almost always looked horrendous (granted, so did a couple of the yellow/gold kits), and I'll always think of black as a United color. No matter what the club claims, next season's away kit sure looks black.
But the club claims it's charcoal. Charcoal gray. And the difference between gray and black might actually matter. Liverpool have never finished better than 5th wearing black (sample size: 2) and never worse than 2nd in silver or gray. So which is it?
Post hoc ergo propter hoc. Q.E.D.
You can find images of all of Liverpool's kits here and here.