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