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