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)(11,16)(12,13)(14,19)(15,17)(18,24)(20,21)(22,23)(25,26,31,29)(27,32,28,35)(30,33,38,37)(34,39,36,40)(3,7)(5,8)(9,11)(10,16)(12,22)(13,23)(14,17)(15,19)(18,20)(21,24)(26,29)(32,35)(33,37)(39,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(10,17)(11,19)(13,24)(20,22)(25,27,31,28)(26,32,29,35)(30,34,38,36)(33,39,37,40)(1,3,4,7)(2,5,6,8)(9,12,15,18)(10,13,17,24)(11,20,19,22)(14,23,16,21)(25,28,31,27)(26,32,29,35)(30,34,38,36)(33,40,37,39)(1,2)(3,5)(4,6)(7,8)(9,13)(10,18)(11,21)(12,17)(14,20)(15,24)(16,22)(19,23)(25,29,31,26)(27,32,28,35)(30,37,38,33)(34,39,36,40)(9,14)(10,19)(11,17)(12,21)(13,20)(15,16)(18,23)(22,24)(25,30,31,38)(26,33,29,37)(27,34,28,36)(32,39,35,40)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.