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