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