Almost thirty years ago my father brought back home a small ornamental apple that he had picked up while travelling for his job. I extracted the seeds and sowed them. I kept four seedlings, eventually planting three in my parents front garden. When the resulting trees finally flowered and set fruit one had fruit like an ordinary crab apple (similar in appearance to an ordinary dessert apple but much smaller), another had very small bright yellow fruit and the final one had very small bright red fruit. This was the biggest variability (considering it was such a small sample!) I have ever come across.
Since then my mother has passed away and my father has moved. However at least one of the trees was still there a few years ago – sadly probably not now though.
Below is an old photo of the red variety.