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