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