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