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