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