One vertex per element, one color per generator, with an edge from x to x·s.
(9,10)(11,17)(12,15)(13,16)(14,19)(18,23)(20,22)(21,24)(25,26)(27,36)(28,34)(29,35)(30,33)(31,39)(32,37)(38,40) involution — undirected(1,2)(3,7)(4,8)(5,6)(9,11)(10,14)(12,18)(13,19)(15,21)(16,17)(20,24)(22,23)(25,27,29,39)(26,31,35,36)(28,38,30,37)(32,33,40,34)(2,6)(7,8)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(25,27)(26,32)(28,37)(29,39)(30,38)(31,34)(33,36)(35,40)(1,3,5,4)(2,7,6,8)(10,16)(14,17)(15,22)(21,23)(25,28,29,30)(26,33,35,34)(27,37,39,38)(31,32,36,40)(1,4,5,3)(2,7,6,8)(11,19)(14,17)(18,24)(21,23)(25,28,29,30)(26,34,35,33)(27,38,39,37)(31,32,36,40)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.