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