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