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