Different types of natural slate

[Simeon]

I've just reroofed a house down the country and the old slates measure 24 x 14. These look grey/black on the weathered side but the unexposed sides are a kind of claret. I'd like to reuse them elsewhere but am at a loss as to their name. Have spent the last hour Googling but to no avail.

 

[Guest117]

Blue Bangor ??

 

[Simeon]

Thanks Badge ........ but can they be blue bangor on one side and pink bangor on t'other?