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