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