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