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