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