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