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