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