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