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