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