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