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