Lat. niger once again

In view of the fact that Lat. niger means practically the same as Gk.
eremnos 'murky, black, dark', I'd like to propose an etymology:

*h1regW-no-s > pre-Lat. *regnos > *rignos > *nigros (metathesis) > niger

Advantages:

(1) It explains the /i/, which is not accounted for by the assumption of
*negW-ro- (*e > Lat. i before <gn> [Nn], as in <dignus, lignum> but
_not_ before /gr/).

(2) <niger> has an external cognate with the same meaning.

Piotr