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