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