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