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