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