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