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