Last year I germinated dozens of seedling from a dark red rosetted Sempervivum. Few of them look like the parent and I have started selecting the most promising.
The first one I potted up separately is quite large, with long narrow leaves and it is already producing offsets. Because it is quite hairy raindrops collect on the leaves and stand out clearly against the greyish background of the leaves. (The mother plant is in the top right of the picture).
My other houseleeks do not seem to do this, at least not in any obvious way.
My second selection is much smaller, but with similarly coloured leaves. These, however, are distinctively fringed with long white hairs and the leaf edges seem to curl in somewhat, which enhances the hairy nature of the rosette.