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