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