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