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