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