after seeing the featured guitar this month(Rosie),with the ebony faceplate on the headstock... I imagined a fretboard with frets that were anodized or ? to a dark color,essentially giving the look of a fretless instrument from afar.
  Is this possible or do you think  that any treatment wouldn't be permanent enough,
...any inlays would surely stand out  against a dark dark fretboard. : )
 thanks for thoughts,
Kris

What an interesting idea!

Since the frets are usually sanded and shaped after getting installed on the fingerboard, I don't think it's possible as this would go through the plating or anodizing before the instrument is even played.
 
The frets would need to be made out of a dark material so the color was good all the way through.