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