The MacOS colorpicker has an eyedropper tool that can grab colors from anywhere on screen.
How might that be achieved on Windows?
anywhere on screen.
from other apps or desktop i guess today you need a screen read permission by user.
there are few win api methods you find in MSDN docu. Device Context / GetPixel
or one of the Xojo MBS Plugin?
or in your own Xojo App windows via Picture .RGBSurface .Pixel(x,y)
alternative let the user load a picture in Xojo.