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