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