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