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