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