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