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