On Weblio, the same dictionary says 紅{くれない} means "crimson" (deep red) and 紅{べに} means "vermilion" (bright red). Another dictionary says 紅{くれない}, 紅{べに}, 紅{こう} are all nouns, but I thought こう couldn't be used alone.
If 紅 is just one colour, then the difference between that and 紅色 is the same between 白 and 白色.
Is 紅色 more commonly read as こうしょく, くれないいろ or べにいろ? Does こういろ exist? I know 訓{くん}読{よ}み is preferred when speaking normally, but こうしょく seems the main pronunciation.