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