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