Grt Britain KeVII One Shilling Color Difference

Concerning what 'shades' do and do not exist, always consider there are two or three reasons for the existence of 'shades.'

Some are intentional, such as the change from blue-green to yellow-green in this series (the 4d and 6d Wildings also had intentional changes).
Some are due to the work being done at another location (Machin shades by Harrison/De La Rue) or by another printer. De La Rue lost the contract for printing UK stamps to Harrison. Provisional printings were executed by Harrison and the Stamp Printing Branch of the IRS (better known as 'Somerset House' where they were located. The latter had the technology for printing stamps in more than one colour. The IRS also printed the monocoloured stamps that had frequent use as revenue stamps (6d, high values).
Most, however, are due to the mixing of ink for a print run. This was done manually, and colours were matched visually.

It is astounding Harrison, but more so the IRS managed to produce a wider range of 'shades' in two years than De La Rue in almost a decade.

For this stamp, De La Rue used a dull green ink and a carmine ink. The IRS used green and scarlet ink. At a later time, De La Rue mixed an ink that was scarlet rather than carmine, and the IRS mix at some time came out carmine rather than scarlet.

I am not a fan of Scott when it comes to European stamps. As a basic listing, it may be fine. When they try to be somewhat more specialised, they are not so good. Looking at the Scott listing provided by Partime, I get the impression Scott misses the point that De La Rue's greens were dull green, and the IRS was not a dull but purer green.

No light green is listed by Stanley Gibbons. I would expect them to list such a recognisable 'shade.' I agree with Noocassel the lighter greens in Floortrader's image are faded.

I agree for a very large part with Floortrader's statement there are 'a few shades of green in this stamp.' Mine are not all 'shades' listed by Stanley Gibbons. They list one for De La Rue on ordinary paper and an additional deep dull green on chalk-surfaced paper. For the IRS-printings, they list green, deep green and dark green. However, this is not an exhaustive list as even within one definition, there may have been several printings resulting in slightly different shades just not recognised.

I have no idea whether Scott's light green is a lighter appearance of the green used by the IRS or just a dull green used by De La Rue. If they list these 'shades' as Partime mentions, they, completely, miss the point of the greens being part of how to identify the printers.