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