I have never seen the leather turn purple only the cloth, you should be fine should you use them. Do you think you can resell them for what you paid? $950 gets you a good start on the way to Recaro's.
Used Recaro's $500 (they can be found for much less)
Sliders $270 (new)
Planted bases $280 (new)
If you want them recovered an outfit on eBay, zoomzooming or some such, makes a quality German vinyl replacement set for $500 and offers leather as well.
Cheers and good luck either way!
You seem to quite knowledgeable when it comes to those seats! $500 for recaros? show me where!? lol BTW do you happen to know if the TMI's reproduction seats also sit high like the corbeaus? I believe they are reproductions of the recaros if I am not mistaken?