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