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