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