The Saakshin Vishnu was, strictly speaking, a witness. The rich black colour, krishna in old Sanskrit, was testimony to its provenance, that this God hailed from before the beginning of time. Before even light was created. For before light was created, all was dark. All was black. The absence of hands signified that He would not enact any karma of His own. The absence of legs showed that He would not move, either towards you or away from you. He was neutral. He would take no sides in petty human rivalries. He was beyond personal likes and dislikes.