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)(13,14,18,23)(15,24,27,20)(16,28,19,21)(17,22,25,26)(5,7)(6,9)(8,12)(10,11)(13,14)(15,25)(16,21)(17,27)(18,23)(19,28)(20,26)(22,24) involution — undirected(2,4)(7,12)(9,11)(13,15,16,22,18,27,19,26)(14,20,28,17,23,24,21,25)(6,10)(9,11)(13,16,18,19)(14,21,23,28)(15,26,27,22)(17,24,25,20)(13,17,16,24,18,25,19,20)(14,22,28,27,23,26,21,15)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.