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