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