I’ve managed to find a way to re-colour in green my Manjaro GNOME (in case you’re interested, I installed this extension: This GNOME Extension Brings 'Material You' to Linux Desktops - OMG! Ubuntu!), but the login screen, although properly branded with the Manjaro logo, is still in Adwaita blue since the switch to Gnome 42.
Was it a deliberate choice that of not colouring it in green? Will it change in the future? Is there a way to change the accent colour?
Not a super-pressing issue, but any help is appreciated.
And for the login screen you could use Login Manager Settings, but there a few steps required, which could easily break gdm (tools->extract default theme->edit css file yourself), not recommended.