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