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