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)(27,36)(28,35)(38,39)(3,7)(5,8)(9,10)(11,14)(12,15)(13,16)(17,22)(18,23)(19,21)(20,24)(25,26)(27,32)(28,34)(29,35)(30,31)(33,36)(37,39)(38,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,10,13,16)(11,14,18,23)(12,15,21,19)(17,22,20,24)(25,27,30,36)(26,32,31,33)(28,37,35,40)(29,38,34,39)(1,3,4,7)(2,5,6,8)(9,10)(11,14)(12,19)(13,16)(15,21)(17,24)(18,23)(20,22)(25,27)(26,33)(28,37)(29,39)(30,36)(31,32)(34,38)(35,40)(1,2)(3,5)(4,6)(7,8)(9,11,13,18)(10,14,16,23)(12,20,21,17)(15,24,19,22)(25,28)(26,34)(27,37)(29,31)(30,35)(32,39)(33,38)(36,40)(9,12,13,21)(10,15,16,19)(11,17,18,20)(14,22,23,24)(25,29,30,34)(26,35,31,28)(27,38,36,39)(32,40,33,37)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.