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