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