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