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