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