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