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