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