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