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