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