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