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)(13,14,20,25,19,17,18,23)(15,24,26,21,27,16,22,28)(5,6)(7,11)(8,10)(9,12)(13,15,19,27)(14,21,17,28)(16,25,24,23)(18,26,20,22)(2,4)(5,7)(6,9)(8,12)(10,11)(13,16)(14,22)(15,25)(17,26)(18,21)(19,24)(20,28)(23,27) involution — undirected(7,12)(9,11)(13,17,20,23,19,14,18,25)(15,24,26,21,27,16,22,28)(6,10)(9,11)(13,18,19,20)(14,23,17,25)(15,26,27,22)(16,28,24,21)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.