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