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