This is a good example of a production piece - where artists work collaboratively, often with an agreed colour palette, or background patter or colour. In this case they all agreed to do faces that are looking out of the wall. You can see in the middle three pieces there is a co-ordination of colour there as well, less the case with the outer pieces.
Subset are an extremely active and politically motivated collective based in Dublin. They agreed to paint at 2018 Hit the North festival even though all the budget for the festival was already allocated when the opportunity to paint this site came up. They agreed to paint for no fee and cover all their own expenses such was their desire to paint this wall at Hit the North.