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