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