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