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