In London, the name 'Green Line' has been used for over 80 years to market cross london and suburban coach services, offering higher standards of comfort and reliability to passangers.
Route 757, linking Luton airport and central London has been marketed for years as a Green Line services.
Arriva the Shires- the operator- linked with EasyJet airlines, a cut price airline to market the route to Easyjet passangers.
for most people, this is a downgrade in marketing terms. Easyjet amd Ryanair are regarded as 'cheap and cheerful' airlines in the UK, offering cheap fares and far from good service.
[personally I do not mind- I use both airlines quite a lot!