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