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