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