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