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