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