One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(13,14)(15,23)(16,22)(17,19)(18,21)(20,24)(25,28)(26,27) involution — undirected(1,2,3,4)(5,6)(7,11)(8,10)(9,12)(14,19)(20,27)(21,22)(23,28)(5,7)(6,9)(8,12)(10,11)(13,15,17,25)(14,20,19,27)(16,24,18,26)(21,23,22,28)(7,12)(9,11)(13,16,17,18)(14,21,19,22)(15,24,25,26)(20,23,27,28)(6,10)(9,11) involution — undirectedA 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.