A Listing Question - Great Britain Qv Officials - Army

So I see that this one is listed as " blue - green ". SG O42

The 1 two look blue green to me, but the right most looks more of a green. Guessing they are all "blue green" , O42 ?

On my monitor the right hand stamp appears to be the typical color, green. The center stamp appears to be bright blue, possibly a result of some type of chemical reaction. The left stamp is transitioning to bright blue. I have seen this occur with other green colored stamps.

But for this listing , theres only one color , right?

All three stamps are colour changelings. The one on the right shows somewhat of the correct colour, but is affected.

In old Stanley Gibbons catalogues, you may find the basic "Jubilee" stamp in the blue colour. It was delisted after it was shown to be a colour changeling. The (yellow) zinc chromate pigment used in later printings of the stamp is soluble in water and causes the stamp to become blue when soaked.

Thank you. I remeber seeing somewhere about these changlings, but did not remember where. Thanks for your example. I had thought the one on the right was the furtherest away from the correct color. But if I rember the color descriptions correctly when 2 colors are used, the 1st listed color is the descriptor and the second is the primary color. Hence blue-green would be more green with blue note.

Oops - so O42 is the correct listing??

Specialised L37 = Concise O42, indeed.