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