HgCl2 is white when pure. the zygoat synth will result in pretty dirty looking HgCl2, but it works the same.
to test take a tiny crumb of HgCl2 in a few mls of MeOH and add a pieces of Al foil, if it amalgamates, you have it right.
by amalgamate i mean the solvent will turn cloudy grey as the Al slowly dissolves