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