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)(15,17)(16,21)(18,20)(19,24)(22,25)(23,27)(26,28) involution — undirected(1,2)(3,4)(6,10)(11,12)(14,15)(16,23)(18,25)(19,27)(21,28)(24,26) involution — undirected(2,4)(13,15,17,14)(16,21,24,19)(18,22,25,20)(23,27,26,28)(2,4)(5,7,9,8)(6,11,10,12)(13,16,17,24)(14,19,15,21)(18,26,25,23)(20,27,22,28)(5,8,9,7)(6,11,10,12)(14,15)(19,21)(20,22)(27,28)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.