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