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