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