The lines that do best here are the affectionate ones: puns about rainbows and Pride, written from inside the community rather than about it.
Read the room as you would anywhere. A playful line at a Pride party or a queer bar is part of the fun; the same line to someone whose orientation you are only guessing at puts them in an awkward spot.
Pride events, queer bars and clubs, dating apps and group chats full of friends who will rate your attempt out of ten. These lines also make good cards and messages for partners, especially around Pride month or an anniversary.
Keep them kind. The best LGBTQ+ lines celebrate rather than single anyone out, and they work as well between long-term partners as between strangers. If you are not sure whether someone is interested, a friendly conversation will tell you more than any line can.

