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