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