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