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