Initially, I was only assuming that this man was the son of Joseph Gray because of the transfer of land from Joseph to Samuel as shown in the Griffiths Valuation. However, BB found their marriage in Maghera Meeting House, and it shows he was indeed the son of a Joseph Gray of Camus.
There are two Joseph Greys in Camus in the GV, one a labourer with no land, the other holding Plot 33 of 27 acres which passes to a Samuel Grey circa 1861 who already holds Plot 35a of 12 acres plus Plot 38 of 1 acre jointly with James Hynes, both also in Camus in the circa 1855 Griffiths Valuation. All of Samuel's land passes to non Grays: William Patterson got Plot 33 in 1879 and Samuel Martin got Plot 35a and 38, also in 1879. Since this Samuel died in 1878, it must be he who owned all three plots: 33, 35a and 38 and therefore the two Samuels in the GV for Camus are the same person.
There are two other samuel Grays in Camus that I know of, one probably the son of the other. The younger one is probably too young to be in the GV but the older one should be but is not. I do not know why.