how to color merkins white chocolate to sliver/grey

I add black chocolate disks to my white when I melt it to get grey.  It doesn't take much and black is now available year round.  You can also use regular food color gel or paste, it just might sieze the chocolate, to which I would either add paramont crystals or a little shortening to loosen it back up again. The only other option I can think of it to dust the chocolate with the non-toxic silver dust after it's molded.

Actually I mean the colored disks.  They sell all different colors of the disks.  I think the chocolate ones will just give you a light brown.  I mix different colors of chocolate disks to get new colors, like red and brown to get a brick color.  If you can't find black, I would the gel food color and thin with shortening or paramont crystals if it siezes.

I just did silver shells and jewlerly.  I use the silver luster dust and also the silver spray paint from either Wilton or Duff.  I get the Duff products at Michaels craft store.  They look great

You have to brush on dusts after it's molded to get a sparkle.....colorings don't give sparkle.

That is an option, and the one I do the most.  I dry dusted my chocolate with the silver lustre dust and it worked well.   You can paint with orange oil and silver lustre dust to get a great shine and covereage (and it tastes really yummy).  I haven't used the airbrush spray so the others can help you with that.