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