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