English speakers are pretty confusing talking about the clarity of liquids. Often colorless, clear liquids are called "white" (like white rum). Transparent brown liquids (whiskey) some people will say are not "clear", which they reserve for the colorless liquids. There's a word "limpid" which might be useful though definitions sometimes mean just transparent or both transparent and colorless.

The author suggests it's something like the clarity that Homer was observing and that's been my assumption for a while. It's unsurprising that we're confused what the word might've meant, given how imprecise we are about similar topics.