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