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