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)(11,17)(12,15)(13,16)(14,20)(18,22)(19,24)(21,23)(25,26,29,33,30,34,35,39)(27,31,37,32,28,38,36,40)(2,5)(6,7)(9,11,18,19,12,20,13,21)(10,14,22,23,15,17,16,24)(25,27,35,36,30,28,29,37)(26,31,39,40,34,38,33,32)(11,19)(13,18)(14,23)(16,22)(17,24)(20,21)(25,28,30,27)(26,32,34,40)(29,37,35,36)(31,39,38,33)(1,3,4,8)(2,6,5,7)(10,15)(14,17)(16,22)(23,24)(25,29,30,35)(26,33,34,39)(27,36,28,37)(31,40,38,32)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.