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