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