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