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