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