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