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