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