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