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)(15,18)(16,21)(17,20)(19,23)(22,25)(24,27)(26,28) involution — undirected(2,4)(5,7,8,11)(6,9,10,12)(13,15,18,14)(16,21,23,19)(17,22,25,20)(24,27,28,26)(6,10)(7,11)(13,16)(14,19)(15,21)(17,24)(18,23)(20,26)(22,27)(25,28) involution — undirected(6,10)(9,12)(14,15)(19,21)(20,22)(26,27) involution — undirected(16,23)(19,21)(24,28)(26,27) involution — undirected(13,17,18,25)(14,20,15,22)(16,24,23,28)(19,26,21,27)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.