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