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