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