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)(15,20)(16,21)(17,22)(18,23)(19,25)(24,27)(26,28) involution — undirected(5,7)(6,9)(8,11)(10,12)(13,15,18,26)(14,19,23,27)(16,25,17,24)(20,21,28,22)(2,4)(7,11)(9,12)(13,15)(14,20)(16,24)(17,25)(18,26)(19,22)(21,27)(23,28) involution — undirected(7,11)(9,12)(13,16,18,17)(14,21,23,22)(15,24,26,25)(19,20,27,28)(6,10)(9,12)(13,16,18,17)(14,22,23,21)(15,25,26,24)(19,20,27,28)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.