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