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