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