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