Because the name, common green grasshopper (Omocestus viridulus), implies that this is a common, green grasshopper there is a tendency to think all common, green grasshoppers are common green grasshoppers! I know that is ambiguous so let me explain!
Of the few grasshopper species that occur in Dorset, or in the British Isles if it comes to that, there are more than one species that are green. Not only is the common green green but so too is the meadow, the stripe-winged, the two marsh grasshoppers and the female mottled grasshopper. My point is that not all green grasshoppers are common green grasshoppers. Secondly, there are species of grasshopper that are more common than the common green, notably the meadow and the common field. Hopefully you are beginning to understand what my opening statement meant!
Whilst widespread in Dorset this species is restricted to areas where the grass is quite long and it occurs mainly on the chalk although it can be found on the grassy areas of the Purbeck coast and the Purbeck Ridge. That said, it can be found elsewhere, on grassy woodland rides for example.
To me, this species sums up everything that is difficult about identifying grasshoppers. Several species are so alike and several species can have considerable variation within the same species; it really is a job for the expert. The rest of us just have to do the best we can!