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