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