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