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