selection by colour

I am 99.9 percent sure there is no such feature:( but is it possible to select parts of a mesh based on a colour like in a paint application where you can for instance select only the green sceen

you can select by material !

select face then select menu and select material

happy bl

L will select what’s linked to the item you’re hovering the mouse over. The tools panel pops up options for how the selection is limited with material, and seams being two handy options. Also in the object’s material properties panel, while in edit mode, you can select or deselect all faces assigned to a material.