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