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