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)(13,14,18,22,17,21,25,28)(15,16,20,24,23,19,26,27)(5,6)(7,10)(8,11)(9,12)(13,15)(14,16)(17,23)(18,20)(19,21)(22,24)(25,26)(27,28) involution — undirected(2,4)(5,7,9,8)(6,10,12,11)(13,15)(14,19)(16,21)(17,23)(18,20)(22,27)(24,28)(25,26)(5,7,9,8)(6,11,12,10)(15,23)(16,19)(20,26)(24,27)(5,8,9,7)(6,11,12,10)(13,16,18,24,17,19,25,27)(14,20,22,23,21,26,28,15)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.