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