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