In the early 1960's the Werco Drum Company of Chicago started production of an open backed Banjolele with a blue sparkly body and an aluminium neck. They only made the one model, it was called the Blue Sparkle so always blue and production of the Banjolele had stopped by 1970. 

There are a number of questions with this Banjolele that I don't know the answer to though. In 1950 the Grossman Music Co. started selling an all metal Banjolele called the Dixie and this instrument was clearly made with the same patented neck and tailpiece. Production of the Dixie appears to have ended before Werco started making the Blue Sparkle, (which had a wooden body), but if there is a connection between Werco and Grossman I haven't found it yet?