Can’t decide?

I’m 24. Going to my bf’s cousins wedding in March. The venue is quite fancy and the weather is normal pretty chilly here around this time of year.

I have only met his parents and sisters and that’s it. I haven’t met his relatives and that. And lately a few cousins started adding me on social media.

I can’t decide what colour to wear. I’m definitely going for a midi dress that is fitted. Should I go for:

1. Red- strong sexy independent look
2. Black- safe, a bit boring, predictable but elegant and still attractive
3. Floral (something out of ted baker or phase eight)- Fun, cute, down to earth, cheerful
4. Green- safe, standard
5. Royal blue- strong, smart, shows that I have a good career maybe?

Please I need some input from you ladies :)