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