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