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