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