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