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)(13,14,17,18)(15,19,20,16)(21,22)(23,27)(24,28)(25,26)(6,10)(11,12)(14,18)(16,19)(22,26)(23,28) involution — undirected(5,7,9,8)(6,11,10,12)(13,15)(14,16)(17,20)(18,19)(21,23,25,28)(22,27,26,24)(1,2)(3,4)(5,8,9,7)(6,11,10,12)(13,15)(14,19)(16,18)(17,20)(21,24)(22,23)(25,27)(26,28)(5,6)(7,11)(8,12)(9,10)(13,16,17,19)(14,20,18,15)(21,22)(23,27)(24,28)(25,26)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.