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