|Orange brown (Die 1 only)|
There is also this shade which is the result of a chemical reaction taking place between mercury salts in the composition of the vermilion ink and the copper electrotype. The result is that the electro suffers damage and the colour of the stamp changes to a yellow / orange shade. Normally you see this on the QOEENSLAND variety stamps like this one above. I would imagine that the reason why these have survived and non-variety types have not is the monetary value of this variety.
Prestige Philately auctioned the "Colonel Harrie Evans" Colonies and Pacific Islands collection on 4th May 2002. Auction 96, Lot 378 was listed as "Crown/Q (Wmk '6') 1d orange-yellow (the colour of the 4d), cleaned fiscal cancel. Offered "as is". [Colonel Evans identified this stamp and quoted from Oceania (1898) which stated that a single 1d cliché was inserted in error in the 4d plate and that the mistake was corrected early in the printing]." Auction page here.
Another example of a yellowish shade, seen on Ebay