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