Chris, I'm offering an opinion here, but I think that you will find that unless they are a hybrid, you will see yellow or pale yellow flowers (all the way to white). We also need to be careful to define what we are talking about when we say "flower color" as you sometimes need to distinguish between the petals and the sepals. So I think the petals of heuffelii flowers are typically yellow or pale yellow. There are hybrids between sempervivum and J. heuffelii, some commonly known as Sempervivum types, which could incorporate a different flower color.
A major thing is that heuffelii flowers, like the rest of the Jovibarba, have fewer petals than Sempervivum, which makes the flowers distinctive and helps to ID the jovis.
I did a search on the internet to see if I could find a mention of other colors for heuffelii flowers and could not locate any. Personally, I'd love to see a bright orange flowering variety as I think that would be possible down the road and quite nice.
I've had at least a dozen different named types flower for me and none have had any other colors so far.