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