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