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