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