One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6)(7,11)(8,10)(9,12)(14,18)(15,22)(19,24)(23,27) involution — undirected(5,7)(6,9)(8,12)(10,11)(14,19)(15,23)(17,20)(18,24)(21,25)(22,27) involution — undirected(2,4)(7,12)(9,11)(13,14,20,24,16,18,17,19)(15,21,27,28,22,25,23,26)(6,10)(9,11)(15,22)(21,25)(23,27)(26,28) involution — undirected(13,15,20,27,16,22,17,23)(14,21,24,28,18,25,19,26)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.