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