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