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