No, there is no strict requirement to wear white trousers/shorts/skirts - if your club uniform does not specify what colour of trousers, etc constitute the uniform "bottoms."
White trousers are becoming increasingly difficult to purchase, and this was one reason the AA Natioinal Judges uniform was changed from white to fawn trousers/slacks/skirts/shorts. Some archers still wear white trousers (or even all white) but this is becoming increasingly rare sight these days.
As far as the uniform bottoms are concerned, it would not be a good idea to arrive at the event in baggy cargo trousers or shorts. Neat attire is considered acceptable - even at National Championships. In the southern states, the winter wear is generally track suit pants, jeans (neat) or dressy trousers - so long as the tops are either club, state, national uniform that's OK with the organising committees.
Second Question: In relation to cardigans, sweaters, coats etc what colours and styles are acceptable? If the weather is inclement (raining) is there a desired colour and style for protective rain wear?
A good question! In Victoria archers generally wear rugby tops or polo fleece pullovers or jackets, and even track suit jackets. Many polo fleece jackets now come with zip out sleeves, and these are considered acceptable. Colours generally are not really taken into account. As far as wet weather clothing is concerned, anything goes - from gortex to nylon or plastic. Any colour is acceptable for rain wear.
Third Question: What colour and style of shoes or boots are acceptable wear?
Generally, shoes or boots must have enclosed toe areas on the front. Sport shoes/runners are very popular and many archers wear sturdy hiking style boots in either gortex or leather. Sandals or thongs are not permitted, mainly for safety reasons............
..............I can assure you though, the Dress Regulations have been generally relaxed by many, many organising committees, even (as stated above) at national Championships. Jeans were once considered a big no no but, are now considered almost a fashion item for many people both young and old consequently, they have been allowed at events Australia wide. Organising committees generally make the statement "may be enforced" to cover themselves in case someone arrives looking dirty and untidy; which them gives them the option to deny the person entry to the tournament.
Personally, I believe if you wear your club polo shirts and neat tidy trousers and suitable shoes, there really shouldn't be a probem. Should the OC deny you entry, there is (or should be) the right of appeal to the Jury of Appeal."