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