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