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