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