People these days seem to wear plain, smart or smart/ casual clothes in darker colours. So navy, dark purple, dark green , maroon , dark brown. Men and women often wear white shirts / blouses / tops with dark trousers or skirts. Often beige raincoats ( when needed ).
So defo not all black ( unless that’s been requested by the family of course).
I think the only “ definitely not “ are too casual ( trainers, denim unless very plain and dark, too revealing ( short shorts or skirts, plunging necklines , crop tops, spaghetti straps with underwear showing ) , too attention seeking ( very bright patterns and bold colours ) and sportswear or tee shirts with big logos.
Unless of course there’s been a request from the family “ John loved Star Wars so wear your favourite star wars tee shirt “ etc .
I’m going to a funeral next week ( no one close ) and will wear a navy linen dress, which is very loose so hopefully not too hot .
I hope you find something that works for you @Fleetheart