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