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