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)(11,19)(12,23)(13,24)(14,18)(15,22)(16,21)(17,20)(25,26,31,28)(27,32,38,35)(29,39,37,33)(30,34,36,40)(1,3,4,8)(2,5,6,7)(9,11)(10,15)(12,20)(13,21)(14,22)(16,17)(18,19)(23,24)(25,27)(26,32)(28,35)(29,36)(30,37)(31,38)(33,34)(39,40)(1,3)(2,5)(4,8)(6,7)(25,26,31,28)(27,35,38,32)(29,33,37,39)(30,34,36,40)(1,3)(2,5)(4,8)(6,7)(9,12,14,21)(10,16,18,23)(11,20,22,13)(15,17,19,24)(25,28,31,26)(27,35,38,32)(29,39,37,33)(30,34,36,40)(1,2)(3,5)(4,6)(7,8)(9,13,14,20)(10,17,18,24)(11,21,22,12)(15,16,19,23)(25,29,31,37)(26,33,28,39)(27,36,38,30)(32,34,35,40)(9,10)(11,15)(12,23)(13,17)(14,18)(16,21)(19,22)(20,24)(25,30,31,36)(26,34,28,40)(27,37,38,29)(32,33,35,39)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.