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