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)(15,23)(16,26)(17,21)(18,24)(19,20)(22,28)(25,27) involution — undirected(1,2,4,3)(6,11)(7,8)(10,12)(13,15,17,20)(14,19,21,23)(16,24,27,22)(18,26,28,25)(5,6,7,10,9,12,8,11)(13,16,18,19,17,27,28,23)(14,20,22,26,21,15,24,25)(1,3,4,2)(6,12)(10,11)(14,21)(16,27)(19,23)(22,24)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.