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