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