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