Plants differ in the broadness of the colored edge or center. It may be a change in the number of cells in the meristem contributing to the different layers. Despite all of the above there are for sure other cases and exceptions, but the above covers the most encountered ones. Summary Mutation is an event that changes DNA which its offspring inherits and this can be in the flower and in a bud, and both in the nucleus or in the chloroplast. Recombination is an event that exchanges part of chromosomes leading to green or white in a yellow plant.
Chimaeral rearrangement is an event whereby cells are exchanged between layers differing in color.
Sports are changes in a bud only and can be due to recombinations, chimaeral rearrangements or rarely new mutations. Most of what we see as variation in offsets is due to recombination or chimaeral rearrangements and only rarely will mutations be involved. Notwithstanding that, both recombination or chimaeral rearrangements can only take place if a mutation has taken place earlier and so provided the ground to play on. This article reprinted with permission from the American Hosta Society.