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