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