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