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