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)(15,22)(16,21)(17,24)(18,23)(19,25)(20,26)(27,28) involution — undirected(1,2,3,4)(13,15,17,26,19,27,18,16)(14,20,23,22,25,21,24,28)(6,9)(10,12)(13,16,19,26)(14,21,25,20)(15,17,27,18)(22,24,28,23)(13,15)(14,22)(16,17)(18,26)(19,27)(20,23)(21,24)(25,28) involution — undirected(5,7,8,11)(6,10,9,12)(13,17,19,18)(14,23,25,24)(15,16,27,26)(20,28,21,22)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.