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