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