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