I know many institutions require signatures with Blue ink for the reason stated but it makes no sense anymore in the days of color photocopies.Many businesses require blue ink for documents. This distinguishes the writing from a black photocopy.
DITTOI personally think most of the requirements/reasons are BS.
I say this because when I was working, I was frequently in an environment wherein certain things couldn't be done which made getting a wet signature difficult.
I had a digital copy of my signature and I would paste it into documents.
Never had one rejected.