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