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