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