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