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