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)(11,19)(12,23)(13,24)(14,18)(15,22)(16,21)(17,20)(26,28)(31,34)(32,36)(38,40) involution — undirected(1,2,4,6)(3,5,8,7)(9,11)(10,15)(12,20)(13,21)(14,22)(16,17)(18,19)(23,24)(27,33)(31,34)(35,39)(38,40)(1,2)(3,5)(4,6)(7,8)(25,26,30,28)(27,31,33,34)(29,32,37,36)(35,38,39,40)(1,3,4,8)(2,5,6,7)(9,12,14,21)(10,16,18,23)(11,20,22,13)(15,17,19,24)(25,27,30,33)(26,31,28,34)(29,35,37,39)(32,38,36,40)(9,13,14,20)(10,17,18,24)(11,21,22,12)(15,16,19,23)(25,28,30,26)(27,34,33,31)(29,36,37,32)(35,40,39,38)(9,10)(11,15)(12,23)(13,17)(14,18)(16,21)(19,22)(20,24)(25,29,30,37)(26,32,28,36)(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.