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