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