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