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