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