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