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