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