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