A dazzling assortment of pet colors exist in Continental Giants
As all recognized colors were developed by dedicated breeders, the same can be said for unrecognized (pet) colors.
While not showable, one cannot deny the beauty of a Siamese Sable or Harlequin conti. Responsible breeders work to perfect and be able to reliably reproduce new or rare colors. Some do require that all going to pet homes be neutered/spayed to prevent mixing with recognized colors, others leave it to the new owner to make the right choice in terms of breeding later on.
When new colors are developed, great expense and time is taken to develop the color (Several recognized colors have been developed and maintained for well over 100 years). It may take 5 or more generations and dozens of breedings to arrive at a quality conti with the desired coloring. Lagomorph color genetics are studied, careful notes taken and all this with great expense in housing and feed, not a simple undertaking.
It is important to note that as a new color is worked on the type of the conti (structure, size, confirmation) my well be lacking even once the color is perfected. From that point the breeder works to increase any deficits through even more breedings while maintaining the hard earned color. It is equally important to recognize that many color genetic traits are very difficult to remove from a line once established (Vienna Marking for example). Many generations later unexpected colored babies will be born (also referred to as popouts).