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