how do you know what colour dogs to put together in cavaliers

Join the breed clubs and ask the successful, experienced breeders.
:)

It is usual to breed the parti colours together & the solids, but depending on what breeding is behind the dogs a mixture of parti & solid can produce correctly marked dogs but & it is a very big but you must know in great detail what is behind the dogs before even thinking about mixing the partis & solids

Hi The Cavalier King charles Spaniel, the World of dogs by Margaret Workman. has a Colour Breeding chart, which tells you what colour to go with and the colours you will get.it is a very good book.