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