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