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