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