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