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