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