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