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