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