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