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