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