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