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