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