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