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