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