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