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