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