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