Sample Color tool. Eyedropper reverts to a pointer In the Shader editor if I click to change the colour in one of the colour swatch windows on a Principled node and then select the eyedropper or Colour Sample tool, as soon as I move the mouse it reverts to a pointer and won't allow me to select a colour from an adjacent Image Editor window.
See the gif below, it's a little difficult to describe.
I've worked it out, it's not an error after all. Once you select the Eyedropper, when you move the mouse the cursor will revert to a pointer, however the next click will change the color wherever you click in the Blender window. Just not immediately intuitive because the cursor doesn't remain as a pipette.