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