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)(15,24)(16,23)(17,25)(18,20)(19,22)(21,28)(26,27) involution — undirected(1,2)(3,4)(6,9)(10,12)(13,15,18,25)(14,17,20,24)(16,26,19,21)(22,27,23,28)(5,7,8,11)(6,10,9,12)(13,16)(14,20)(15,25)(17,28)(18,19)(24,27)(2,4)(13,17,18,24)(14,21,20,26)(15,23,25,22)(16,27,19,28)(6,9)(10,12)(13,16,18,19)(14,22,20,23)(15,26,25,21)(17,27,24,28)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.