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