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