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