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