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