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