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