Is eyedropper or color picker available in libreoffice ?
As far as I’m aware, you cannot pick a colour from, say a photo, and apply it to a drawing object in the way that you can in Inkscape or Gimp. I believe this workaround is the nearest you can get unless you use an external tool Color picker eyedropper?
You can choose any hex value colour you like by number or from a continuous palette. The Clone Formatting tool can be handy for colouring objects the same as another.
For Impress and Draw, see answers at Is there any method or tool for pick up color in LibreOffice Draw?.