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