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