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