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