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)(15,22)(16,27)(17,21)(18,20)(19,26)(23,28)(24,25) involution — undirected(1,2,4,3)(6,9)(10,12)(13,15)(14,19)(16,25)(17,26)(18,23)(20,24)(21,22)(27,28)(1,3,4,2)(5,7,8,11)(6,10,9,12)(15,23)(16,18)(19,24)(20,27)(22,28)(25,26)(13,14)(15,24)(16,20)(17,21)(18,27)(19,23)(22,25)(26,28) involution — undirected(13,16,17,18)(14,20,21,27)(15,25,26,23)(19,24,22,28)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.