Lynn & Blue, You would call the plant that resulted "seedling of Red Rubin" if you only knew one of the parents, in this case the seed parent. If you knew the pollen parent as well, then you could list it as a cross between the two.
If the resulting plant was different enough from all of the other thousands of cultivars, then it would be appropriate to give it a name. Sometimes a grower will number the plants being evaluated and the number might stick to a successful variety. For example, Purdy's cultivars come in a selection of numbered varieties (as well as Big Red!). The numbering schemes, of course, depend on the person creating the plants.
Speaking of variegated sempervivums, there have been a few examples seen. However, I don't think any of them lasted too long or were very successful. A healthy, variegated semp would be a nice addition to the hobby. Personally, I hope to never see a polka-dotted one.
