I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
There is not a way to encourage a mutation as you described, however maybe we can direct you to a source that would have a variety that fits your description. The following sources sell bougainvilleas and have many varieties. They could perhaps identify your mystery plant from an e-mailed description:
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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