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