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