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