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