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