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