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