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