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