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