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