[PentaxLou]

I know you said the super tak 7 element also has 6 iris blades but it is over complicating things to bring the later models in. The 8 elements were only ever super taks.
I have 4 x 8 elements and none of them show any yellowing at all. I think you can state "if there is any yellowing then it is not an 8 element". Unless of course someone here says they have one.
I find the IR mark the defining feature to look for followed up by the rear element. But the rear element takes a bit of experience to be sure of yourself.

I have two of the eight-element lenses and they are both yellowed.

[kypfer]

I have 4 x 8 elements and none of them show any yellowing at all. I think you can state "if there is any yellowing then it is not an 8 element". Unless of course someone here says they have one.
I find the IR mark the defining feature to look for followed up by the rear element. But the rear element takes a bit of experience to be sure of yourself.

My 8 element 50mm f/1.4 "looks yellow" with some purple reflections … whether that's 'yellowing' or yellow-coloured coating I don't know how to tell.
When compared to contemporary 35mm f/3.5 and 135mm f/3.5 Super-Takumar lenses, these two look decidedly "neutral".
I write "contemporary" because all three were bought with a Spotmatic, as a set, in a local general auction, so they may well have been 'one-owner from new'.