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