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