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