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