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