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