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