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