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