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