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