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