so as not to disappoint all those entering here in the same boat as ayc:
The colour of Her Majesty’s clothes is never made known in advance, so don’t be tempted to telephone the Household before an event to make sure that you aren’t wearing the same colour or that your choice of outfit with clash with The Queen’s.
Morning dress for men consists of a grey or black morning coat with a grey or yellow waistcoat and striped grey trousers. A top hat should be worn, and grey or yellow gloves (matching your waistcoat of course!) should be carried. Ladies are in this case expected to wear smart day dress: a suit or dress with hat and gloves, high heels, and a handbag to complete the outfit. Lounge suits are just plain business suits and are now the form for the majority of occasions; again, smart day dress is the correct outfit for ladies. Black tie calls for dinner jackets to be worn with a smart bow tie. Ladies should wear an evening or cocktail dress (it is best not to wear black, which is really only appropriate only when the Court is in mourning). Finally, white tie involves an evening tail coat with white bow tie and waistcoat for men and long evening dresses with long gloves and best jewellery including tiaras for the ladies. Orders and decorations are worn by everyone entitled to do so, though it is important not to wear the collar of an order (these never appear after sunset).