Hello Red,
Thank you for asking here!
Basically, what everyone else said!

It is always safest to ask in a quiet moment. The other safe option is to simply use the first name a person gave. It my sound a bit odd at first, but like that you can be certain to get it right.
You very welcome to read here and ask questions! We've had a few incidents where we felt a cisgendered person blamed us for making things unnecessarily complicated when it comes to language (such a mine field!). But normally we're fun to be with [emoji16]