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