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