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