Mark,
From what I’ve read on Jag-Lovers it seems that it’s easy to get confused about some of the interior colours Jaguar used, as their names don’t necessarily align well with current perceptions of what to expect. There are beige, cinnamon, biscuit, light tan, and tan interior colours, and judging by self-entered information in xkedata there is considerable confusion as to which is which. Here is one data point from a post here with photos of swatches of beige, cinnamon and biscuit:
I understand that “light tan” has a strong orange component (check out posts from @harvey_ferris on his interior, like this one: Early Tan interior for 64 FHC - #5 by Harvey_Ferris) and that “tan” is much darker than one might assume, being almost a tobacco colour.
The reason I mention all this is that the answer to your question may depend of whether you mean “Jaguar Cinnamon” or some other colour that is a cinnamon colour in your mind’s eye, so to speak. WIth regards to Opalescent Dark Blue and Cinnamon, you might want to look at photos of this car: https://bringatrailer.com/listing/1966-jaguar-xke-roadster-32/. The seller describes the interior as “tan”, but I suspect that this is “tan” in a generic sense, rather than a Jaguar Tan. IN some of the photos, it looks more like the Cinnamon swatch I linked to earlier, though in others it looks more orange - maybe Light Tan? In the end, the best advice may be to get sample swatches from several interior vendors (they won’t be the same) and view a lot of photos… Good luck.