One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,3)(12,15,16,24)(13,18,19,23)(14,22,21,27)(17,25,20,26)(2,3)(5,9)(8,10)(14,21)(17,20)(22,27)(25,26) involution — undirected(4,6,7,11)(5,8,9,10)(6,11)(8,10)(12,14)(13,17)(15,22)(16,21)(18,25)(19,20)(23,26)(24,27) involution — undirected(4,5)(6,10)(7,9)(8,11)(12,13,16,19)(14,20,21,17)(15,23,24,18)(22,25,27,26)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.