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