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