also: べに · こう
Refers to a vivid, deep red color, often with poetic or traditional connotations. Commonly read くれない in this sense.
She wore a deep red dress.
The sky dyed crimson is beautiful.
Only with reading べに
Specifically refers to cosmetic rouge or lipstick, read べに. Often used in compounds like 口紅 (くちべに, lipstick).
My mother is applying lipstick in front of the mirror.
The western sky turned crimson with the sunset.
She put on a little rouge before going out.
On-reading, mostly found in compounds such as 紅茶 (こうちゃ) or 紅葉 (こうよう). Rare as a standalone word.