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