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