Lipstick
noun, の adjective
A mouth deep red is a deep red you put on your mouth. This is lipstick.
くちべに
This uses kun'yomi readings for both of the kanji. You already know this for 口, but you haven't learned either of the kun'yomi readings for 紅 yet, so here's a mnemonic to help you memorize the one you'll need for this vocab: Your favorite lipstick is one called Benny (べに) by... Benny. There's a guy called Benny that makes really pretty lipstick, he's just not great at naming things, so it's all just Benny.
口紅をポケットに入れっぱなしにしてたみたいで、乾燥機の中で溶けちゃったのよね。
I left my lipstick in my pocket and it melted in the dryer.