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)(15,23)(16,21)(17,22)(18,26)(19,25)(20,24)(27,28) involution — undirected(1,2)(3,4)(6,10)(11,12)(13,15,19,16)(14,21,25,23)(17,20,27,18)(22,26,28,24)(5,7,9,8)(6,11,10,12)(13,16,18,17,19,15,20,27)(14,22,24,21,25,28,26,23)(2,4)(5,8,9,7)(6,12,10,11)(13,17,20,16,19,27,18,15)(14,23,26,28,25,21,24,22)(6,10)(11,12)(13,18,19,20)(14,24,25,26)(15,17,16,27)(21,22,23,28)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.