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