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