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