This thread, in particular the first 5d diadem scan on page 1, has caught the attention of the Australian board.
It has been mentioned that the 5d diadem on piece is a forgery and on closer inspection it is. This forgeries site gives every indication that this one is by Oneglia:https://stampforgeries.com/new-sout...en-victoria/
I found the image on stampauctionnetwork. It was part of the Neal Allen collection (Shreves #61 April 3, 2004, lot 478) and was again auctioned by Dutch Country Auctions last year (sale #316, lot 782). The description in both auctions stated that the stamp came with a 1988 PF certificate! Caveat emptor indeed.....
Robson Lowe (Australasia p.40) lists the two shades: dull green - slightly bluish & dull green. He offered no price for the former in used condition. He states the former "is usually found with the watermark inverted and reversed, but there is little difference in the two shades when in unused condition."
The scans below are from the Alvorado collection, auctioned by Spink in 2010. They hopefully will offer some indication of the shade difference.