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