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