The Blue Men

According to their page on the Beltane Fire Society's website, the Blue Men are elders, and keepers of wisdom, rather than warriors:

The Blue Manís role is both practical and spiritual. Queens come and go, the King is killed and reborn each year, but the Blue Man is constant. He keeps the collected wisdom of the Court, the knowledge of the ritual, and maintains the order required by nature.
He leads the Court through a spiritual landscape primed with pitfalls to see the summer safely brought about with the death - and subsequent rebirth - of the Green Man.
Those who play the part of blue men carry out a similar role in real life during the run up to the events. They visit each of the performance groups in turn to explain the rituals and the narrative of the performance. They offer support and guidance to both organisers and performers alike and encourage all involved to focus on the task ahead.

To an extent, the function of the steward is to assist the Blues as they guide the Procession around the Hill, and this aspect of the role is often reflected in the stewards' face paint.