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