I would wear long boots, light colourd jods, shirt and tie or stock, and tweed or black jacket. That said i used to see people out cubbing looking alot more relaxed than that, some wearing navy jods with a tweed jacked, others just in fairly normal ridding clothes, depends who your out with i guess.
If it was very wet i used to wear a waterproof coat over my tweed jacket sometimes too.
As I am a complete newbie and don't own a tweed jacket have been told as long as i'm smart is ok so thinking white breeches don't own beige /yellow as showjump will wear white show shirt my jacket is grey pin striped may wear it under everyday whitaker riding jacket but odviously don't want it wrecked!! and odviously long boots would think is different depending on what hunt you go with? I would phone secertary and ask what is acceptable