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