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